all these changes

frontend/node_modules/rbush/LICENSE

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+MIT License
+
+Copyright (c) 2016 Vladimir Agafonkin
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

frontend/node_modules/rbush/README.md

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+RBush
+=====
+
+RBush is a high-performance JavaScript library for 2D **spatial indexing** of points and rectangles.
+It's based on an optimized **R-tree** data structure with **bulk insertion** support.
+
+*Spatial index* is a special data structure for points and rectangles
+that allows you to perform queries like "all items within this bounding box" very efficiently
+(e.g. hundreds of times faster than looping over all items).
+It's most commonly used in maps and data visualizations.
+
+[![Build Status](https://travis-ci.org/mourner/rbush.svg?branch=master)](https://travis-ci.org/mourner/rbush)
+[![](https://img.shields.io/badge/simply-awesome-brightgreen.svg)](https://github.com/mourner/projects)
+
+## Demos
+
+The demos contain visualization of trees generated from 50k bulk-loaded random points.
+Open web console to see benchmarks;
+click on buttons to insert or remove items;
+click to perform search under the cursor.
+
+* [randomly clustered data](http://mourner.github.io/rbush/viz/viz-cluster.html)
+* [uniformly distributed random data](http://mourner.github.io/rbush/viz/viz-uniform.html)
+
+## Install
+
+Install with NPM (`npm install rbush`), or use CDN links for browsers:
+[rbush.js](https://unpkg.com/rbush@2.0.1/rbush.js),
+[rbush.min.js](https://unpkg.com/rbush@2.0.1/rbush.min.js)
+
+## Usage
+
+### Creating a Tree
+
+```js
+var tree = rbush();
+```
+
+An optional argument to `rbush` defines the maximum number of entries in a tree node.
+`9` (used by default) is a reasonable choice for most applications.
+Higher value means faster insertion and slower search, and vice versa.
+
+```js
+var tree = rbush(16);
+```
+
+### Adding Data
+
+Insert an item:
+
+```js
+var item = {
+    minX: 20,
+    minY: 40,
+    maxX: 30,
+    maxY: 50,
+    foo: 'bar'
+};
+tree.insert(item);
+```
+
+### Removing Data
+
+Remove a previously inserted item:
+
+```js
+tree.remove(item);
+```
+
+By default, RBush removes objects by reference.
+However, you can pass a custom `equals` function to compare by value for removal,
+which is useful when you only have a copy of the object you need removed (e.g. loaded from server):
+
+```js
+tree.remove(itemCopy, function (a, b) {
+    return a.id === b.id;
+});
+```
+
+Remove all items:
+
+```js
+tree.clear();
+```
+
+### Data Format
+
+By default, RBush assumes the format of data points to be an object
+with `minX`, `minY`, `maxX` and `maxY` properties.
+You can customize this by providing an array with corresponding accessor strings
+as a second argument to `rbush` like this:
+
+```js
+var tree = rbush(9, ['[0]', '[1]', '[0]', '[1]']); // accept [x, y] points
+tree.insert([20, 50]);
+```
+
+If you're indexing a static list of points (you don't need to add/remove points after indexing), you should use [kdbush](https://github.com/mourner/kdbush) which performs point indexing 5-8x faster than RBush.
+
+### Bulk-Inserting Data
+
+Bulk-insert the given data into the tree:
+
+```js
+tree.load([item1, item2, ...]);
+```
+
+Bulk insertion is usually ~2-3 times faster than inserting items one by one.
+After bulk loading (bulk insertion into an empty tree),
+subsequent query performance is also ~20-30% better.
+
+Note that when you do bulk insertion into an existing tree,
+it bulk-loads the given data into a separate tree
+and inserts the smaller tree into the larger tree.
+This means that bulk insertion works very well for clustered data
+(where items in one update are close to each other),
+but makes query performance worse if the data is scattered.
+
+### Search
+
+```js
+var result = tree.search({
+    minX: 40,
+    minY: 20,
+    maxX: 80,
+    maxY: 70
+});
+```
+
+Returns an array of data items (points or rectangles) that the given bounding box intersects.
+
+Note that the `search` method accepts a bounding box in `{minX, minY, maxX, maxY}` format
+regardless of the format specified in the constructor (which only affects inserted objects).
+
+```js
+var allItems = tree.all();
+```
+
+Returns all items of the tree.
+
+### Collisions
+
+```js
+var result = tree.collides({minX: 40, minY: 20, maxX: 80, maxY: 70});
+```
+
+Returns `true` if there are any items intersecting the given bounding box, otherwise `false`.
+
+
+### Export and Import
+
+```js
+// export data as JSON object
+var treeData = tree.toJSON();
+
+// import previously exported data
+var tree = rbush(9).fromJSON(treeData);
+```
+
+Importing and exporting as JSON allows you to use RBush on both the server (using Node.js) and the browser combined,
+e.g. first indexing the data on the server and and then importing the resulting tree data on the client for searching.
+
+Note that the `nodeSize` option passed to the constructor must be the same in both trees for export/import to work properly.
+
+### K-Nearest Neighbors
+
+For "_k_ nearest neighbors around a point" type of queries for RBush,
+check out [rbush-knn](https://github.com/mourner/rbush-knn).
+
+## Performance
+
+The following sample performance test was done by generating
+random uniformly distributed rectangles of ~0.01% area and setting `maxEntries` to `16`
+(see `debug/perf.js` script).
+Performed with Node.js v6.2.2 on a Retina Macbook Pro 15 (mid-2012).
+
+Test                         | RBush  | [old RTree](https://github.com/imbcmdth/RTree) | Improvement
+---------------------------- | ------ | ------ | ----
+insert 1M items one by one   | 3.18s  | 7.83s  | 2.5x
+1000 searches of 0.01% area  | 0.03s  | 0.93s  | 30x
+1000 searches of 1% area     | 0.35s  | 2.27s  | 6.5x
+1000 searches of 10% area    | 2.18s  | 9.53s  | 4.4x
+remove 1000 items one by one | 0.02s  | 1.18s  | 50x
+bulk-insert 1M items         | 1.25s  | n/a    | 6.7x
+
+## Algorithms Used
+
+* single insertion: non-recursive R-tree insertion with overlap minimizing split routine from R\*-tree (split is very effective in JS, while other R\*-tree modifications like reinsertion on overflow and overlap minimizing subtree search are too slow and not worth it)
+* single deletion: non-recursive R-tree deletion using depth-first tree traversal with free-at-empty strategy (entries in underflowed nodes are not reinserted, instead underflowed nodes are kept in the tree and deleted only when empty, which is a good compromise of query vs removal performance)
+* bulk loading: OMT algorithm (Overlap Minimizing Top-down Bulk Loading) combined with Floyd–Rivest selection algorithm
+* bulk insertion: STLT algorithm (Small-Tree-Large-Tree)
+* search: standard non-recursive R-tree search
+
+## Papers
+
+* [R-trees: a Dynamic Index Structure For Spatial Searching](http://www-db.deis.unibo.it/courses/SI-LS/papers/Gut84.pdf)
+* [The R*-tree: An Efficient and Robust Access Method for Points and Rectangles+](http://dbs.mathematik.uni-marburg.de/publications/myPapers/1990/BKSS90.pdf)
+* [OMT: Overlap Minimizing Top-down Bulk Loading Algorithm for R-tree](http://ftp.informatik.rwth-aachen.de/Publications/CEUR-WS/Vol-74/files/FORUM_18.pdf)
+* [Bulk Insertions into R-Trees Using the Small-Tree-Large-Tree Approach](http://www.cs.arizona.edu/~bkmoon/papers/dke06-bulk.pdf)
+* [R-Trees: Theory and Applications (book)](http://www.apress.com/9781852339777)
+
+## Development
+
+```bash
+npm install  # install dependencies
+
+npm test     # check the code with JSHint and run tests
+npm run perf # run performance benchmarks
+npm run cov  # report test coverage (with more detailed report in coverage/lcov-report/index.html)
+```
+
+## Compatibility
+
+RBush should run on Node and all major browsers. The only caveat: IE 8 needs an [Array#indexOf polyfill](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf#Polyfill) for `remove` method to work.
+
+## Changelog
+
+#### 2.0.1 — June 29, 2016
+
+- Fixed browser builds in NPM.
+
+#### 2.0.0 — June 29, 2016
+
+- **Breaking:** changed the default format of inserted items from `[20, 40, 30, 50]` to `{minX: 20, minY: 40, maxX: 30, maxY: 50}`.
+- **Breaking:** changed the `search` method argument format from `[20, 40, 30, 50]` to `{minX: 20, minY: 40, maxX: 30, maxY: 50}`.
+- Improved performance by up to 30%.
+- Added `equalsFn` optional argument to `remove` to be able to remove by value rather than by reference.
+- Changed the source code to use CommonJS module format. Browser builds are automatically built and published to NPM.
+- Quickselect algorithm (used internally) is now a [separate module](https://github.com/mourner/quickselect).
+
+#### 1.4.3 — May 17, 2016
+
+- Fixed an error when inserting many empty bounding boxes.
+
+#### 1.4.2 — Dec 16, 2015
+
+- 50% faster insertion.
+
+#### 1.4.1 — Sep 16, 2015
+
+- Fixed insertion in IE8.
+
+#### 1.4.0 — Apr 22, 2015
+
+- Added `collides` method for fast collision detection.
+
+#### 1.3.4 — Aug 31, 2014
+
+- Improved bulk insertion performance for a large number of items (e.g. up to 100% for inserting a million items).
+- Fixed performance regression for high node sizes.
+
+#### 1.3.3 — Aug 30, 2014
+
+- Improved bulk insertion performance by ~60-70%.
+- Improved insertion performance by ~40%.
+- Improved search performance by ~30%.
+
+#### 1.3.2 — Nov 25, 2013
+
+- Improved removal performance by ~50%. [#18](https://github.com/mourner/rbush/pull/18)
+
+#### 1.3.1 — Nov 24, 2013
+
+- Fixed minor error in the choose split axis algorithm. [#17](https://github.com/mourner/rbush/pull/17)
+- Much better test coverage (near 100%). [#6](https://github.com/mourner/rbush/issues/6)
+
+#### 1.3.0 — Nov 21, 2013
+
+- Significantly improved search performance (especially on large-bbox queries — up to 3x faster). [#11](https://github.com/mourner/rbush/pull/11)
+- Added `all` method for getting all of the tree items. [#11](https://github.com/mourner/rbush/pull/11)
+- Made `toBBox`, `compareMinX`, `compareMinY` methods public, made it possible to avoid Content Security Policy issues by overriding them for custom format. [#14](https://github.com/mourner/rbush/pull/14) [#12](https://github.com/mourner/rbush/pull/12)
+
+#### 1.2.5 — Nov 5, 2013
+
+- Fixed a bug where insertion failed on a tree that had all items removed previously. [#10](https://github.com/mourner/rbush/issues/10)
+
+#### 1.2.4 — Oct 25, 2013
+
+- Added Web Workers support. [#9](https://github.com/mourner/rbush/pull/9)
+
+#### 1.2.3 — Aug 30, 2013
+
+- Added AMD support. [#8](https://github.com/mourner/rbush/pull/8)
+
+#### 1.2.2 — Aug 27, 2013
+
+- Eliminated recursion when recalculating node bboxes (on insert, remove, load).
+
+#### 1.2.0 — Jul 19, 2013
+
+First fully functional RBush release.

frontend/node_modules/rbush/index.js

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+'use strict';
+
+module.exports = rbush;
+module.exports.default = rbush;
+
+var quickselect = require('quickselect');
+
+function rbush(maxEntries, format) {
+    if (!(this instanceof rbush)) return new rbush(maxEntries, format);
+
+    // max entries in a node is 9 by default; min node fill is 40% for best performance
+    this._maxEntries = Math.max(4, maxEntries || 9);
+    this._minEntries = Math.max(2, Math.ceil(this._maxEntries * 0.4));
+
+    if (format) {
+        this._initFormat(format);
+    }
+
+    this.clear();
+}
+
+rbush.prototype = {
+
+    all: function () {
+        return this._all(this.data, []);
+    },
+
+    search: function (bbox) {
+
+        var node = this.data,
+            result = [],
+            toBBox = this.toBBox;
+
+        if (!intersects(bbox, node)) return result;
+
+        var nodesToSearch = [],
+            i, len, child, childBBox;
+
+        while (node) {
+            for (i = 0, len = node.children.length; i < len; i++) {
+
+                child = node.children[i];
+                childBBox = node.leaf ? toBBox(child) : child;
+
+                if (intersects(bbox, childBBox)) {
+                    if (node.leaf) result.push(child);
+                    else if (contains(bbox, childBBox)) this._all(child, result);
+                    else nodesToSearch.push(child);
+                }
+            }
+            node = nodesToSearch.pop();
+        }
+
+        return result;
+    },
+
+    collides: function (bbox) {
+
+        var node = this.data,
+            toBBox = this.toBBox;
+
+        if (!intersects(bbox, node)) return false;
+
+        var nodesToSearch = [],
+            i, len, child, childBBox;
+
+        while (node) {
+            for (i = 0, len = node.children.length; i < len; i++) {
+
+                child = node.children[i];
+                childBBox = node.leaf ? toBBox(child) : child;
+
+                if (intersects(bbox, childBBox)) {
+                    if (node.leaf || contains(bbox, childBBox)) return true;
+                    nodesToSearch.push(child);
+                }
+            }
+            node = nodesToSearch.pop();
+        }
+
+        return false;
+    },
+
+    load: function (data) {
+        if (!(data && data.length)) return this;
+
+        if (data.length < this._minEntries) {
+            for (var i = 0, len = data.length; i < len; i++) {
+                this.insert(data[i]);
+            }
+            return this;
+        }
+
+        // recursively build the tree with the given data from scratch using OMT algorithm
+        var node = this._build(data.slice(), 0, data.length - 1, 0);
+
+        if (!this.data.children.length) {
+            // save as is if tree is empty
+            this.data = node;
+
+        } else if (this.data.height === node.height) {
+            // split root if trees have the same height
+            this._splitRoot(this.data, node);
+
+        } else {
+            if (this.data.height < node.height) {
+                // swap trees if inserted one is bigger
+                var tmpNode = this.data;
+                this.data = node;
+                node = tmpNode;
+            }
+
+            // insert the small tree into the large tree at appropriate level
+            this._insert(node, this.data.height - node.height - 1, true);
+        }
+
+        return this;
+    },
+
+    insert: function (item) {
+        if (item) this._insert(item, this.data.height - 1);
+        return this;
+    },
+
+    clear: function () {
+        this.data = createNode([]);
+        return this;
+    },
+
+    remove: function (item, equalsFn) {
+        if (!item) return this;
+
+        var node = this.data,
+            bbox = this.toBBox(item),
+            path = [],
+            indexes = [],
+            i, parent, index, goingUp;
+
+        // depth-first iterative tree traversal
+        while (node || path.length) {
+
+            if (!node) { // go up
+                node = path.pop();
+                parent = path[path.length - 1];
+                i = indexes.pop();
+                goingUp = true;
+            }
+
+            if (node.leaf) { // check current node
+                index = findItem(item, node.children, equalsFn);
+
+                if (index !== -1) {
+                    // item found, remove the item and condense tree upwards
+                    node.children.splice(index, 1);
+                    path.push(node);
+                    this._condense(path);
+                    return this;
+                }
+            }
+
+            if (!goingUp && !node.leaf && contains(node, bbox)) { // go down
+                path.push(node);
+                indexes.push(i);
+                i = 0;
+                parent = node;
+                node = node.children[0];
+
+            } else if (parent) { // go right
+                i++;
+                node = parent.children[i];
+                goingUp = false;
+
+            } else node = null; // nothing found
+        }
+
+        return this;
+    },
+
+    toBBox: function (item) { return item; },
+
+    compareMinX: compareNodeMinX,
+    compareMinY: compareNodeMinY,
+
+    toJSON: function () { return this.data; },
+
+    fromJSON: function (data) {
+        this.data = data;
+        return this;
+    },
+
+    _all: function (node, result) {
+        var nodesToSearch = [];
+        while (node) {
+            if (node.leaf) result.push.apply(result, node.children);
+            else nodesToSearch.push.apply(nodesToSearch, node.children);
+
+            node = nodesToSearch.pop();
+        }
+        return result;
+    },
+
+    _build: function (items, left, right, height) {
+
+        var N = right - left + 1,
+            M = this._maxEntries,
+            node;
+
+        if (N <= M) {
+            // reached leaf level; return leaf
+            node = createNode(items.slice(left, right + 1));
+            calcBBox(node, this.toBBox);
+            return node;
+        }
+
+        if (!height) {
+            // target height of the bulk-loaded tree
+            height = Math.ceil(Math.log(N) / Math.log(M));
+
+            // target number of root entries to maximize storage utilization
+            M = Math.ceil(N / Math.pow(M, height - 1));
+        }
+
+        node = createNode([]);
+        node.leaf = false;
+        node.height = height;
+
+        // split the items into M mostly square tiles
+
+        var N2 = Math.ceil(N / M),
+            N1 = N2 * Math.ceil(Math.sqrt(M)),
+            i, j, right2, right3;
+
+        multiSelect(items, left, right, N1, this.compareMinX);
+
+        for (i = left; i <= right; i += N1) {
+
+            right2 = Math.min(i + N1 - 1, right);
+
+            multiSelect(items, i, right2, N2, this.compareMinY);
+
+            for (j = i; j <= right2; j += N2) {
+
+                right3 = Math.min(j + N2 - 1, right2);
+
+                // pack each entry recursively
+                node.children.push(this._build(items, j, right3, height - 1));
+            }
+        }
+
+        calcBBox(node, this.toBBox);
+
+        return node;
+    },
+
+    _chooseSubtree: function (bbox, node, level, path) {
+
+        var i, len, child, targetNode, area, enlargement, minArea, minEnlargement;
+
+        while (true) {
+            path.push(node);
+
+            if (node.leaf || path.length - 1 === level) break;
+
+            minArea = minEnlargement = Infinity;
+
+            for (i = 0, len = node.children.length; i < len; i++) {
+                child = node.children[i];
+                area = bboxArea(child);
+                enlargement = enlargedArea(bbox, child) - area;
+
+                // choose entry with the least area enlargement
+                if (enlargement < minEnlargement) {
+                    minEnlargement = enlargement;
+                    minArea = area < minArea ? area : minArea;
+                    targetNode = child;
+
+                } else if (enlargement === minEnlargement) {
+                    // otherwise choose one with the smallest area
+                    if (area < minArea) {
+                        minArea = area;
+                        targetNode = child;
+                    }
+                }
+            }
+
+            node = targetNode || node.children[0];
+        }
+
+        return node;
+    },
+
+    _insert: function (item, level, isNode) {
+
+        var toBBox = this.toBBox,
+            bbox = isNode ? item : toBBox(item),
+            insertPath = [];
+
+        // find the best node for accommodating the item, saving all nodes along the path too
+        var node = this._chooseSubtree(bbox, this.data, level, insertPath);
+
+        // put the item into the node
+        node.children.push(item);
+        extend(node, bbox);
+
+        // split on node overflow; propagate upwards if necessary
+        while (level >= 0) {
+            if (insertPath[level].children.length > this._maxEntries) {
+                this._split(insertPath, level);
+                level--;
+            } else break;
+        }
+
+        // adjust bboxes along the insertion path
+        this._adjustParentBBoxes(bbox, insertPath, level);
+    },
+
+    // split overflowed node into two
+    _split: function (insertPath, level) {
+
+        var node = insertPath[level],
+            M = node.children.length,
+            m = this._minEntries;
+
+        this._chooseSplitAxis(node, m, M);
+
+        var splitIndex = this._chooseSplitIndex(node, m, M);
+
+        var newNode = createNode(node.children.splice(splitIndex, node.children.length - splitIndex));
+        newNode.height = node.height;
+        newNode.leaf = node.leaf;
+
+        calcBBox(node, this.toBBox);
+        calcBBox(newNode, this.toBBox);
+
+        if (level) insertPath[level - 1].children.push(newNode);
+        else this._splitRoot(node, newNode);
+    },
+
+    _splitRoot: function (node, newNode) {
+        // split root node
+        this.data = createNode([node, newNode]);
+        this.data.height = node.height + 1;
+        this.data.leaf = false;
+        calcBBox(this.data, this.toBBox);
+    },
+
+    _chooseSplitIndex: function (node, m, M) {
+
+        var i, bbox1, bbox2, overlap, area, minOverlap, minArea, index;
+
+        minOverlap = minArea = Infinity;
+
+        for (i = m; i <= M - m; i++) {
+            bbox1 = distBBox(node, 0, i, this.toBBox);
+            bbox2 = distBBox(node, i, M, this.toBBox);
+
+            overlap = intersectionArea(bbox1, bbox2);
+            area = bboxArea(bbox1) + bboxArea(bbox2);
+
+            // choose distribution with minimum overlap
+            if (overlap < minOverlap) {
+                minOverlap = overlap;
+                index = i;
+
+                minArea = area < minArea ? area : minArea;
+
+            } else if (overlap === minOverlap) {
+                // otherwise choose distribution with minimum area
+                if (area < minArea) {
+                    minArea = area;
+                    index = i;
+                }
+            }
+        }
+
+        return index;
+    },
+
+    // sorts node children by the best axis for split
+    _chooseSplitAxis: function (node, m, M) {
+
+        var compareMinX = node.leaf ? this.compareMinX : compareNodeMinX,
+            compareMinY = node.leaf ? this.compareMinY : compareNodeMinY,
+            xMargin = this._allDistMargin(node, m, M, compareMinX),
+            yMargin = this._allDistMargin(node, m, M, compareMinY);
+
+        // if total distributions margin value is minimal for x, sort by minX,
+        // otherwise it's already sorted by minY
+        if (xMargin < yMargin) node.children.sort(compareMinX);
+    },
+
+    // total margin of all possible split distributions where each node is at least m full
+    _allDistMargin: function (node, m, M, compare) {
+
+        node.children.sort(compare);
+
+        var toBBox = this.toBBox,
+            leftBBox = distBBox(node, 0, m, toBBox),
+            rightBBox = distBBox(node, M - m, M, toBBox),
+            margin = bboxMargin(leftBBox) + bboxMargin(rightBBox),
+            i, child;
+
+        for (i = m; i < M - m; i++) {
+            child = node.children[i];
+            extend(leftBBox, node.leaf ? toBBox(child) : child);
+            margin += bboxMargin(leftBBox);
+        }
+
+        for (i = M - m - 1; i >= m; i--) {
+            child = node.children[i];
+            extend(rightBBox, node.leaf ? toBBox(child) : child);
+            margin += bboxMargin(rightBBox);
+        }
+
+        return margin;
+    },
+
+    _adjustParentBBoxes: function (bbox, path, level) {
+        // adjust bboxes along the given tree path
+        for (var i = level; i >= 0; i--) {
+            extend(path[i], bbox);
+        }
+    },
+
+    _condense: function (path) {
+        // go through the path, removing empty nodes and updating bboxes
+        for (var i = path.length - 1, siblings; i >= 0; i--) {
+            if (path[i].children.length === 0) {
+                if (i > 0) {
+                    siblings = path[i - 1].children;
+                    siblings.splice(siblings.indexOf(path[i]), 1);
+
+                } else this.clear();
+
+            } else calcBBox(path[i], this.toBBox);
+        }
+    },
+
+    _initFormat: function (format) {
+        // data format (minX, minY, maxX, maxY accessors)
+
+        // uses eval-type function compilation instead of just accepting a toBBox function
+        // because the algorithms are very sensitive to sorting functions performance,
+        // so they should be dead simple and without inner calls
+
+        var compareArr = ['return a', ' - b', ';'];
+
+        this.compareMinX = new Function('a', 'b', compareArr.join(format[0]));
+        this.compareMinY = new Function('a', 'b', compareArr.join(format[1]));
+
+        this.toBBox = new Function('a',
+            'return {minX: a' + format[0] +
+            ', minY: a' + format[1] +
+            ', maxX: a' + format[2] +
+            ', maxY: a' + format[3] + '};');
+    }
+};
+
+function findItem(item, items, equalsFn) {
+    if (!equalsFn) return items.indexOf(item);
+
+    for (var i = 0; i < items.length; i++) {
+        if (equalsFn(item, items[i])) return i;
+    }
+    return -1;
+}
+
+// calculate node's bbox from bboxes of its children
+function calcBBox(node, toBBox) {
+    distBBox(node, 0, node.children.length, toBBox, node);
+}
+
+// min bounding rectangle of node children from k to p-1
+function distBBox(node, k, p, toBBox, destNode) {
+    if (!destNode) destNode = createNode(null);
+    destNode.minX = Infinity;
+    destNode.minY = Infinity;
+    destNode.maxX = -Infinity;
+    destNode.maxY = -Infinity;
+
+    for (var i = k, child; i < p; i++) {
+        child = node.children[i];
+        extend(destNode, node.leaf ? toBBox(child) : child);
+    }
+
+    return destNode;
+}
+
+function extend(a, b) {
+    a.minX = Math.min(a.minX, b.minX);
+    a.minY = Math.min(a.minY, b.minY);
+    a.maxX = Math.max(a.maxX, b.maxX);
+    a.maxY = Math.max(a.maxY, b.maxY);
+    return a;
+}
+
+function compareNodeMinX(a, b) { return a.minX - b.minX; }
+function compareNodeMinY(a, b) { return a.minY - b.minY; }
+
+function bboxArea(a)   { return (a.maxX - a.minX) * (a.maxY - a.minY); }
+function bboxMargin(a) { return (a.maxX - a.minX) + (a.maxY - a.minY); }
+
+function enlargedArea(a, b) {
+    return (Math.max(b.maxX, a.maxX) - Math.min(b.minX, a.minX)) *
+           (Math.max(b.maxY, a.maxY) - Math.min(b.minY, a.minY));
+}
+
+function intersectionArea(a, b) {
+    var minX = Math.max(a.minX, b.minX),
+        minY = Math.max(a.minY, b.minY),
+        maxX = Math.min(a.maxX, b.maxX),
+        maxY = Math.min(a.maxY, b.maxY);
+
+    return Math.max(0, maxX - minX) *
+           Math.max(0, maxY - minY);
+}
+
+function contains(a, b) {
+    return a.minX <= b.minX &&
+           a.minY <= b.minY &&
+           b.maxX <= a.maxX &&
+           b.maxY <= a.maxY;
+}
+
+function intersects(a, b) {
+    return b.minX <= a.maxX &&
+           b.minY <= a.maxY &&
+           b.maxX >= a.minX &&
+           b.maxY >= a.minY;
+}
+
+function createNode(children) {
+    return {
+        children: children,
+        height: 1,
+        leaf: true,
+        minX: Infinity,
+        minY: Infinity,
+        maxX: -Infinity,
+        maxY: -Infinity
+    };
+}
+
+// sort an array so that items come in groups of n unsorted items, with groups sorted between each other;
+// combines selection algorithm with binary divide & conquer approach
+
+function multiSelect(arr, left, right, n, compare) {
+    var stack = [left, right],
+        mid;
+
+    while (stack.length) {
+        right = stack.pop();
+        left = stack.pop();
+
+        if (right - left <= n) continue;
+
+        mid = left + Math.ceil((right - left) / n / 2) * n;
+        quickselect(arr, mid, left, right, compare);
+
+        stack.push(left, mid, mid, right);
+    }
+}

frontend/node_modules/rbush/package.json

@@ -0,0 +1,55 @@
+{
+  "name": "rbush",
+  "version": "2.0.2",
+  "description": "High-performance 2D spatial index for rectangles (based on R*-tree with bulk loading and bulk insertion algorithms)",
+  "homepage": "https://github.com/mourner/rbush",
+  "repository": {
+    "type": "git",
+    "url": "git://github.com/mourner/rbush.git"
+  },
+  "keywords": [
+    "spatial",
+    "tree",
+    "search",
+    "rectangle",
+    "index",
+    "math"
+  ],
+  "author": "Vladimir Agafonkin",
+  "license": "MIT",
+  "main": "index.js",
+  "jsdelivr": "rbush.js",
+  "unpkg": "rbush.js",
+  "devDependencies": {
+    "benchmark": "^2.1.4",
+    "browserify": "^14.5.0",
+    "eslint": "^4.13.1",
+    "eslint-config-mourner": "^2.0.3",
+    "faucet": "0.0.1",
+    "istanbul": "~0.4.5",
+    "tape": "^4.8.0",
+    "uglify-js": "^3.2.2"
+  },
+  "scripts": {
+    "test": "eslint index.js test/test.js && node test/test.js | faucet",
+    "perf": "node ./bench/perf.js",
+    "cov": "istanbul cover test/test.js -x test/test.js",
+    "build": "browserify index.js -s rbush -o rbush.js",
+    "build-min": "browserify index.js -s rbush | uglifyjs -c warnings=false -m > rbush.min.js",
+    "prepare": "npm run build && npm run build-min"
+  },
+  "files": [
+    "rbush.js",
+    "rbush.min.js"
+  ],
+  "eslintConfig": {
+    "extends": "mourner",
+    "rules": {
+      "new-cap": 0,
+      "consistent-return": 0
+    }
+  },
+  "dependencies": {
+    "quickselect": "^1.0.1"
+  }
+}

frontend/node_modules/rbush/rbush.js

@@ -0,0 +1,626 @@
+(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.rbush = f()}})(function(){var define,module,exports;return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
+'use strict';
+
+module.exports = rbush;
+module.exports.default = rbush;
+
+var quickselect = require('quickselect');
+
+function rbush(maxEntries, format) {
+    if (!(this instanceof rbush)) return new rbush(maxEntries, format);
+
+    // max entries in a node is 9 by default; min node fill is 40% for best performance
+    this._maxEntries = Math.max(4, maxEntries || 9);
+    this._minEntries = Math.max(2, Math.ceil(this._maxEntries * 0.4));
+
+    if (format) {
+        this._initFormat(format);
+    }
+
+    this.clear();
+}
+
+rbush.prototype = {
+
+    all: function () {
+        return this._all(this.data, []);
+    },
+
+    search: function (bbox) {
+
+        var node = this.data,
+            result = [],
+            toBBox = this.toBBox;
+
+        if (!intersects(bbox, node)) return result;
+
+        var nodesToSearch = [],
+            i, len, child, childBBox;
+
+        while (node) {
+            for (i = 0, len = node.children.length; i < len; i++) {
+
+                child = node.children[i];
+                childBBox = node.leaf ? toBBox(child) : child;
+
+                if (intersects(bbox, childBBox)) {
+                    if (node.leaf) result.push(child);
+                    else if (contains(bbox, childBBox)) this._all(child, result);
+                    else nodesToSearch.push(child);
+                }
+            }
+            node = nodesToSearch.pop();
+        }
+
+        return result;
+    },
+
+    collides: function (bbox) {
+
+        var node = this.data,
+            toBBox = this.toBBox;
+
+        if (!intersects(bbox, node)) return false;
+
+        var nodesToSearch = [],
+            i, len, child, childBBox;
+
+        while (node) {
+            for (i = 0, len = node.children.length; i < len; i++) {
+
+                child = node.children[i];
+                childBBox = node.leaf ? toBBox(child) : child;
+
+                if (intersects(bbox, childBBox)) {
+                    if (node.leaf || contains(bbox, childBBox)) return true;
+                    nodesToSearch.push(child);
+                }
+            }
+            node = nodesToSearch.pop();
+        }
+
+        return false;
+    },
+
+    load: function (data) {
+        if (!(data && data.length)) return this;
+
+        if (data.length < this._minEntries) {
+            for (var i = 0, len = data.length; i < len; i++) {
+                this.insert(data[i]);
+            }
+            return this;
+        }
+
+        // recursively build the tree with the given data from scratch using OMT algorithm
+        var node = this._build(data.slice(), 0, data.length - 1, 0);
+
+        if (!this.data.children.length) {
+            // save as is if tree is empty
+            this.data = node;
+
+        } else if (this.data.height === node.height) {
+            // split root if trees have the same height
+            this._splitRoot(this.data, node);
+
+        } else {
+            if (this.data.height < node.height) {
+                // swap trees if inserted one is bigger
+                var tmpNode = this.data;
+                this.data = node;
+                node = tmpNode;
+            }
+
+            // insert the small tree into the large tree at appropriate level
+            this._insert(node, this.data.height - node.height - 1, true);
+        }
+
+        return this;
+    },
+
+    insert: function (item) {
+        if (item) this._insert(item, this.data.height - 1);
+        return this;
+    },
+
+    clear: function () {
+        this.data = createNode([]);
+        return this;
+    },
+
+    remove: function (item, equalsFn) {
+        if (!item) return this;
+
+        var node = this.data,
+            bbox = this.toBBox(item),
+            path = [],
+            indexes = [],
+            i, parent, index, goingUp;
+
+        // depth-first iterative tree traversal
+        while (node || path.length) {
+
+            if (!node) { // go up
+                node = path.pop();
+                parent = path[path.length - 1];
+                i = indexes.pop();
+                goingUp = true;
+            }
+
+            if (node.leaf) { // check current node
+                index = findItem(item, node.children, equalsFn);
+
+                if (index !== -1) {
+                    // item found, remove the item and condense tree upwards
+                    node.children.splice(index, 1);
+                    path.push(node);
+                    this._condense(path);
+                    return this;
+                }
+            }
+
+            if (!goingUp && !node.leaf && contains(node, bbox)) { // go down
+                path.push(node);
+                indexes.push(i);
+                i = 0;
+                parent = node;
+                node = node.children[0];
+
+            } else if (parent) { // go right
+                i++;
+                node = parent.children[i];
+                goingUp = false;
+
+            } else node = null; // nothing found
+        }
+
+        return this;
+    },
+
+    toBBox: function (item) { return item; },
+
+    compareMinX: compareNodeMinX,
+    compareMinY: compareNodeMinY,
+
+    toJSON: function () { return this.data; },
+
+    fromJSON: function (data) {
+        this.data = data;
+        return this;
+    },
+
+    _all: function (node, result) {
+        var nodesToSearch = [];
+        while (node) {
+            if (node.leaf) result.push.apply(result, node.children);
+            else nodesToSearch.push.apply(nodesToSearch, node.children);
+
+            node = nodesToSearch.pop();
+        }
+        return result;
+    },
+
+    _build: function (items, left, right, height) {
+
+        var N = right - left + 1,
+            M = this._maxEntries,
+            node;
+
+        if (N <= M) {
+            // reached leaf level; return leaf
+            node = createNode(items.slice(left, right + 1));
+            calcBBox(node, this.toBBox);
+            return node;
+        }
+
+        if (!height) {
+            // target height of the bulk-loaded tree
+            height = Math.ceil(Math.log(N) / Math.log(M));
+
+            // target number of root entries to maximize storage utilization
+            M = Math.ceil(N / Math.pow(M, height - 1));
+        }
+
+        node = createNode([]);
+        node.leaf = false;
+        node.height = height;
+
+        // split the items into M mostly square tiles
+
+        var N2 = Math.ceil(N / M),
+            N1 = N2 * Math.ceil(Math.sqrt(M)),
+            i, j, right2, right3;
+
+        multiSelect(items, left, right, N1, this.compareMinX);
+
+        for (i = left; i <= right; i += N1) {
+
+            right2 = Math.min(i + N1 - 1, right);
+
+            multiSelect(items, i, right2, N2, this.compareMinY);
+
+            for (j = i; j <= right2; j += N2) {
+
+                right3 = Math.min(j + N2 - 1, right2);
+
+                // pack each entry recursively
+                node.children.push(this._build(items, j, right3, height - 1));
+            }
+        }
+
+        calcBBox(node, this.toBBox);
+
+        return node;
+    },
+
+    _chooseSubtree: function (bbox, node, level, path) {
+
+        var i, len, child, targetNode, area, enlargement, minArea, minEnlargement;
+
+        while (true) {
+            path.push(node);
+
+            if (node.leaf || path.length - 1 === level) break;
+
+            minArea = minEnlargement = Infinity;
+
+            for (i = 0, len = node.children.length; i < len; i++) {
+                child = node.children[i];
+                area = bboxArea(child);
+                enlargement = enlargedArea(bbox, child) - area;
+
+                // choose entry with the least area enlargement
+                if (enlargement < minEnlargement) {
+                    minEnlargement = enlargement;
+                    minArea = area < minArea ? area : minArea;
+                    targetNode = child;
+
+                } else if (enlargement === minEnlargement) {
+                    // otherwise choose one with the smallest area
+                    if (area < minArea) {
+                        minArea = area;
+                        targetNode = child;
+                    }
+                }
+            }
+
+            node = targetNode || node.children[0];
+        }
+
+        return node;
+    },
+
+    _insert: function (item, level, isNode) {
+
+        var toBBox = this.toBBox,
+            bbox = isNode ? item : toBBox(item),
+            insertPath = [];
+
+        // find the best node for accommodating the item, saving all nodes along the path too
+        var node = this._chooseSubtree(bbox, this.data, level, insertPath);
+
+        // put the item into the node
+        node.children.push(item);
+        extend(node, bbox);
+
+        // split on node overflow; propagate upwards if necessary
+        while (level >= 0) {
+            if (insertPath[level].children.length > this._maxEntries) {
+                this._split(insertPath, level);
+                level--;
+            } else break;
+        }
+
+        // adjust bboxes along the insertion path
+        this._adjustParentBBoxes(bbox, insertPath, level);
+    },
+
+    // split overflowed node into two
+    _split: function (insertPath, level) {
+
+        var node = insertPath[level],
+            M = node.children.length,
+            m = this._minEntries;
+
+        this._chooseSplitAxis(node, m, M);
+
+        var splitIndex = this._chooseSplitIndex(node, m, M);
+
+        var newNode = createNode(node.children.splice(splitIndex, node.children.length - splitIndex));
+        newNode.height = node.height;
+        newNode.leaf = node.leaf;
+
+        calcBBox(node, this.toBBox);
+        calcBBox(newNode, this.toBBox);
+
+        if (level) insertPath[level - 1].children.push(newNode);
+        else this._splitRoot(node, newNode);
+    },
+
+    _splitRoot: function (node, newNode) {
+        // split root node
+        this.data = createNode([node, newNode]);
+        this.data.height = node.height + 1;
+        this.data.leaf = false;
+        calcBBox(this.data, this.toBBox);
+    },
+
+    _chooseSplitIndex: function (node, m, M) {
+
+        var i, bbox1, bbox2, overlap, area, minOverlap, minArea, index;
+
+        minOverlap = minArea = Infinity;
+
+        for (i = m; i <= M - m; i++) {
+            bbox1 = distBBox(node, 0, i, this.toBBox);
+            bbox2 = distBBox(node, i, M, this.toBBox);
+
+            overlap = intersectionArea(bbox1, bbox2);
+            area = bboxArea(bbox1) + bboxArea(bbox2);
+
+            // choose distribution with minimum overlap
+            if (overlap < minOverlap) {
+                minOverlap = overlap;
+                index = i;
+
+                minArea = area < minArea ? area : minArea;
+
+            } else if (overlap === minOverlap) {
+                // otherwise choose distribution with minimum area
+                if (area < minArea) {
+                    minArea = area;
+                    index = i;
+                }
+            }
+        }
+
+        return index;
+    },
+
+    // sorts node children by the best axis for split
+    _chooseSplitAxis: function (node, m, M) {
+
+        var compareMinX = node.leaf ? this.compareMinX : compareNodeMinX,
+            compareMinY = node.leaf ? this.compareMinY : compareNodeMinY,
+            xMargin = this._allDistMargin(node, m, M, compareMinX),
+            yMargin = this._allDistMargin(node, m, M, compareMinY);
+
+        // if total distributions margin value is minimal for x, sort by minX,
+        // otherwise it's already sorted by minY
+        if (xMargin < yMargin) node.children.sort(compareMinX);
+    },
+
+    // total margin of all possible split distributions where each node is at least m full
+    _allDistMargin: function (node, m, M, compare) {
+
+        node.children.sort(compare);
+
+        var toBBox = this.toBBox,
+            leftBBox = distBBox(node, 0, m, toBBox),
+            rightBBox = distBBox(node, M - m, M, toBBox),
+            margin = bboxMargin(leftBBox) + bboxMargin(rightBBox),
+            i, child;
+
+        for (i = m; i < M - m; i++) {
+            child = node.children[i];
+            extend(leftBBox, node.leaf ? toBBox(child) : child);
+            margin += bboxMargin(leftBBox);
+        }
+
+        for (i = M - m - 1; i >= m; i--) {
+            child = node.children[i];
+            extend(rightBBox, node.leaf ? toBBox(child) : child);
+            margin += bboxMargin(rightBBox);
+        }
+
+        return margin;
+    },
+
+    _adjustParentBBoxes: function (bbox, path, level) {
+        // adjust bboxes along the given tree path
+        for (var i = level; i >= 0; i--) {
+            extend(path[i], bbox);
+        }
+    },
+
+    _condense: function (path) {
+        // go through the path, removing empty nodes and updating bboxes
+        for (var i = path.length - 1, siblings; i >= 0; i--) {
+            if (path[i].children.length === 0) {
+                if (i > 0) {
+                    siblings = path[i - 1].children;
+                    siblings.splice(siblings.indexOf(path[i]), 1);
+
+                } else this.clear();
+
+            } else calcBBox(path[i], this.toBBox);
+        }
+    },
+
+    _initFormat: function (format) {
+        // data format (minX, minY, maxX, maxY accessors)
+
+        // uses eval-type function compilation instead of just accepting a toBBox function
+        // because the algorithms are very sensitive to sorting functions performance,
+        // so they should be dead simple and without inner calls
+
+        var compareArr = ['return a', ' - b', ';'];
+
+        this.compareMinX = new Function('a', 'b', compareArr.join(format[0]));
+        this.compareMinY = new Function('a', 'b', compareArr.join(format[1]));
+
+        this.toBBox = new Function('a',
+            'return {minX: a' + format[0] +
+            ', minY: a' + format[1] +
+            ', maxX: a' + format[2] +
+            ', maxY: a' + format[3] + '};');
+    }
+};
+
+function findItem(item, items, equalsFn) {
+    if (!equalsFn) return items.indexOf(item);
+
+    for (var i = 0; i < items.length; i++) {
+        if (equalsFn(item, items[i])) return i;
+    }
+    return -1;
+}
+
+// calculate node's bbox from bboxes of its children
+function calcBBox(node, toBBox) {
+    distBBox(node, 0, node.children.length, toBBox, node);
+}
+
+// min bounding rectangle of node children from k to p-1
+function distBBox(node, k, p, toBBox, destNode) {
+    if (!destNode) destNode = createNode(null);
+    destNode.minX = Infinity;
+    destNode.minY = Infinity;
+    destNode.maxX = -Infinity;
+    destNode.maxY = -Infinity;
+
+    for (var i = k, child; i < p; i++) {
+        child = node.children[i];
+        extend(destNode, node.leaf ? toBBox(child) : child);
+    }
+
+    return destNode;
+}
+
+function extend(a, b) {
+    a.minX = Math.min(a.minX, b.minX);
+    a.minY = Math.min(a.minY, b.minY);
+    a.maxX = Math.max(a.maxX, b.maxX);
+    a.maxY = Math.max(a.maxY, b.maxY);
+    return a;
+}
+
+function compareNodeMinX(a, b) { return a.minX - b.minX; }
+function compareNodeMinY(a, b) { return a.minY - b.minY; }
+
+function bboxArea(a)   { return (a.maxX - a.minX) * (a.maxY - a.minY); }
+function bboxMargin(a) { return (a.maxX - a.minX) + (a.maxY - a.minY); }
+
+function enlargedArea(a, b) {
+    return (Math.max(b.maxX, a.maxX) - Math.min(b.minX, a.minX)) *
+           (Math.max(b.maxY, a.maxY) - Math.min(b.minY, a.minY));
+}
+
+function intersectionArea(a, b) {
+    var minX = Math.max(a.minX, b.minX),
+        minY = Math.max(a.minY, b.minY),
+        maxX = Math.min(a.maxX, b.maxX),
+        maxY = Math.min(a.maxY, b.maxY);
+
+    return Math.max(0, maxX - minX) *
+           Math.max(0, maxY - minY);
+}
+
+function contains(a, b) {
+    return a.minX <= b.minX &&
+           a.minY <= b.minY &&
+           b.maxX <= a.maxX &&
+           b.maxY <= a.maxY;
+}
+
+function intersects(a, b) {
+    return b.minX <= a.maxX &&
+           b.minY <= a.maxY &&
+           b.maxX >= a.minX &&
+           b.maxY >= a.minY;
+}
+
+function createNode(children) {
+    return {
+        children: children,
+        height: 1,
+        leaf: true,
+        minX: Infinity,
+        minY: Infinity,
+        maxX: -Infinity,
+        maxY: -Infinity
+    };
+}
+
+// sort an array so that items come in groups of n unsorted items, with groups sorted between each other;
+// combines selection algorithm with binary divide & conquer approach
+
+function multiSelect(arr, left, right, n, compare) {
+    var stack = [left, right],
+        mid;
+
+    while (stack.length) {
+        right = stack.pop();
+        left = stack.pop();
+
+        if (right - left <= n) continue;
+
+        mid = left + Math.ceil((right - left) / n / 2) * n;
+        quickselect(arr, mid, left, right, compare);
+
+        stack.push(left, mid, mid, right);
+    }
+}
+
+},{"quickselect":2}],2:[function(require,module,exports){
+'use strict';
+
+module.exports = quickselect;
+module.exports.default = quickselect;
+
+function quickselect(arr, k, left, right, compare) {
+    quickselectStep(arr, k, left || 0, right || (arr.length - 1), compare || defaultCompare);
+};
+
+function quickselectStep(arr, k, left, right, compare) {
+
+    while (right > left) {
+        if (right - left > 600) {
+            var n = right - left + 1;
+            var m = k - left + 1;
+            var z = Math.log(n);
+            var s = 0.5 * Math.exp(2 * z / 3);
+            var sd = 0.5 * Math.sqrt(z * s * (n - s) / n) * (m - n / 2 < 0 ? -1 : 1);
+            var newLeft = Math.max(left, Math.floor(k - m * s / n + sd));
+            var newRight = Math.min(right, Math.floor(k + (n - m) * s / n + sd));
+            quickselectStep(arr, k, newLeft, newRight, compare);
+        }
+
+        var t = arr[k];
+        var i = left;
+        var j = right;
+
+        swap(arr, left, k);
+        if (compare(arr[right], t) > 0) swap(arr, left, right);
+
+        while (i < j) {
+            swap(arr, i, j);
+            i++;
+            j--;
+            while (compare(arr[i], t) < 0) i++;
+            while (compare(arr[j], t) > 0) j--;
+        }
+
+        if (compare(arr[left], t) === 0) swap(arr, left, j);
+        else {
+            j++;
+            swap(arr, j, right);
+        }
+
+        if (j <= k) left = j + 1;
+        if (k <= j) right = j - 1;
+    }
+}
+
+function swap(arr, i, j) {
+    var tmp = arr[i];
+    arr[i] = arr[j];
+    arr[j] = tmp;
+}
+
+function defaultCompare(a, b) {
+    return a < b ? -1 : a > b ? 1 : 0;
+}
+
+},{}]},{},[1])(1)
+});