diff --git a/vendor/intervaltree/core.js b/vendor/intervaltree/core.js
new file mode 100644
index 0000000000..bcc0f52a9b
--- /dev/null
+++ b/vendor/intervaltree/core.js
@@ -0,0 +1,278 @@
+/**
+ * intervaltree
+ *
+ * @author Andrey Antukh <niwi@niwi.nz>, 2016
+ * @license MIT License <https://opensource.org/licenses/MIT>
+ */
+"use strict";
+
+goog.provide("intervaltree.core");
+goog.provide("intervaltree.core.IntervalTree");
+
+goog.require("goog.asserts");
+goog.require("goog.array");
+
+goog.scope(function() {
+  const assert = goog.asserts.assert;
+  const every = goog.array.every;
+
+  // --- Types Declaration
+
+  class Interval {
+    constructor(start, end, data) {
+      this.start = start;
+      this.end = end;
+      this.data = data || null;
+    }
+
+    toString() {
+      return `v=${this.start},${this.end} d=${this.data}`;
+    }
+  }
+
+  class Node {
+    constructor(interval, parent) {
+      this.interval = interval;
+      this.parent = parent || null
+      this.left = null;
+      this.right = null;
+      this.max = -Infinity;
+    }
+  }
+
+  class IntervalTree {
+    constructor() {
+      this.root = null;
+    }
+
+    add(item) {
+      // Coerce to interval
+      const interval = makeInterval(item);
+
+      // Set root if the current tree is empty
+      if (this.root === null) {
+        this.root = new Node(interval, null);
+      } else {
+        insertInterval(this.root, interval);
+      }
+
+      return this;
+    }
+
+    contains(point) {
+      assert(goog.isNumber(point));
+      assert(this.root !== null);
+      return contains(this.root, point);
+    }
+
+    search(item) {
+      assert(this.root !== null);
+      const interval = makeInterval(item);
+      return search(this.root, interval);
+    }
+  }
+
+  // --- Private Api (Implementation)
+
+  function insertInterval(root, interval) {
+    if (root.interval.start > interval.start) {
+      if (root.left !== null) {
+        insertInterval(root.left, interval);
+      } else {
+        root.left = new Node(interval, root);
+        recalculateMax(root.left);
+      }
+    } else {
+      if (root.right !== null) {
+        insertInterval(root.right, interval);
+      } else {
+        root.right = new Node(interval, root);
+        recalculateMax(root.right);
+      }
+    }
+  }
+
+  function recalculateMax(node) {
+    const interval = node.interval;
+    const parent = node.parent;
+
+    if (parent.max < interval.end) {
+      while (node) {
+        if (node.max < interval.end) {
+          node.max = interval.end;
+        }
+        node = node.parent;
+      }
+    }
+  }
+
+  function contains(root, point) {
+    if (root.interval.start <= point &&
+        root.interval.end >= point) {
+      return true;
+    } else {
+      let result = false;
+
+      if (root.left && root.left.max >= point) {
+        result = result || contains(root.left, point);
+      }
+
+      if (root.right && root.right.max >= point) {
+        result = result || contains(root.right, point);
+      }
+
+      return result;
+    }
+  }
+
+  function isIntervalIntersect(a, b) {
+    return ((a.start <= b.start && a.end >= b.start) ||
+            (a.start <= b.end && a.end >= b.end) ||
+            (b.start <= a.start && b.end >= a.start) ||
+            (b.start <= a.end && b.end >= a.end));
+  }
+
+  function search(root, interval) {
+    console.log("1111");
+    if (isIntervalIntersect(root.interval, interval)) {
+      return root.interval;
+    } else {
+      let result = null;
+
+      if (root.left && root.left.max >= interval.start) {
+        result = result || search(root.left, interval);
+      }
+
+      if (root.right && root.right.max >= interval.start) {
+        result = result || search(root.right, interval);
+      }
+
+      return result;
+    }
+  }
+
+  // --- Public Api
+
+  function makeInterval(value) {
+    if (value instanceof Interval) {
+      return value
+    } else if (goog.isArray(value)) {
+      if (value.length === 1 &&
+          goog.isNumber(value[0])) {
+        return new Interval(value[0], value[0]);
+      } else if (value.length === 2 && goog.isNumber(value[0])) {
+        if (goog.isNumber(value[1])) {
+          return new Interval(value[0], value[1]);
+        } else {
+          return new Interval(value[0], value[0], value[1]);
+        }
+      } else if (value.length === 3 &&
+                 goog.isNumber(value[0]) &&
+                 goog.isNumber(value[1])) {
+        return new Interval(value[0], value[1], value[2]);
+      }
+    } else if (arguments.length === 1 && goog.isNumber(value)) {
+        return new Interval(value, value);
+    } else if (arguments.length >= 2 && goog.isNumber(value)) {
+      if (goog.isNumber(arguments[1])) {
+        return new Interval(value, arguments[1], arguments[2]);
+      } else {
+        return new Interval(value, value, arguments[1]);
+      }
+    } else {
+      throw new Error("Unexpected input.");
+    }
+  };
+
+  function makeTree(items) {
+    const tree = new IntervalTree();
+
+    if (goog.isArrayLike(items)) {
+      for(let item of items) {
+        tree.add(item);
+      }
+    }
+
+    return tree;
+  }
+
+  const module = intervaltree.core;
+
+  // Types
+  module.IntervalTree = IntervalTree;
+  module.Interval = Interval;
+  module.Node = Node;
+
+  // Constructors
+  module.interval = makeInterval;
+  module.create = makeTree;
+
+  // function getRandom(min, max) {
+  //   var crypto = require("crypto");
+  //   var MAX_UINT32 = 0xFFFFFFFF;
+  //   var range = max - min;
+
+  //   if (!(range <= MAX_UINT32)) {
+  //     throw new Error(
+  //       "Range of " + range + " covering " + min + " to " + max + " is > " +
+  //         MAX_UINT32 + ".");
+  //   } else if (min === max) {
+  //     return min;
+  //   } else if (!(max > min)) {
+  //     throw new Error("max (" + max + ") must be >= min (" + min + ").");
+  //   }
+
+  //   // We need to cut off values greater than this to avoid bias in distribution
+  //   // over the range.
+  //   var maxUnbiased = MAX_UINT32 - ((MAX_UINT32 + 1) % (range + 1));
+
+  //   var rand;
+  //   do {
+  //     rand = crypto.randomBytes(4).readUInt32LE();
+  //     // rand = crypto.randomBytes(new Uint32Array(1))[0];
+  //   } while (rand > maxUnbiased);
+
+  //   var offset = rand % (range + 1);
+  //   return min + offset;
+  // }
+
+  // function* randomSeq(n) {
+  //   for(let i=0; i<n; i++) {
+  //     let value = getRandom(0, 1000);
+  //     yield [value, getRandom(value, value+10)]
+  //   }
+  // }
+
+  // function randomList(n) {
+  //   return Array.from(randomSeq(n));
+  // }
+
+  // module.randomList = randomList;
+  // module.benchmark = function() {
+  //   let util = require('util');
+
+  //   const intervals = randomList(100000);
+  //   console.time("init");
+  //   const tree = module.create(intervals);
+  //   console.timeEnd("init");
+
+  //   console.log(util.inspect(tree, {showHidden: false, depth: 5}));
+
+
+  //   console.time("search")
+
+  //   console.log("result:", tree.search(getRandom(0, 100000)));
+
+  //   console.timeEnd("search")
+  // };
+
+  // module.test = function() {
+  //   let util = require('util');
+
+  //   const tree = makeTree([[1,3], [-4,0], [7,8], [6, 100], [8,12]]);
+  //   console.log(util.inspect(tree, {showHidden: false, depth: null}));
+
+  //   console.log("result:", tree.search(8));
+  // };
+
+});