Bump mongodb from 2.2.36 to 3.6.1

Bumps [mongodb](https://github.com/mongodb/node-mongodb-native) from 2.2.36 to 3.6.1.
- [Release notes](https://github.com/mongodb/node-mongodb-native/releases)
- [Changelog](https://github.com/mongodb/node-mongodb-native/blob/master/CHANGES_3.0.0.md)
- [Commits](mongodb/node-mongodb-native@v2.2.36...v3.6.1)

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -32,7 +32,7 @@
   "dependencies": {
     "clone": "^2.1.0",
     "express": "^4.14.0",
-    "mongodb": "^2.2.16",
+    "mongodb": "^3.6.1",
     "optimist": "^0.6.1",
     "pathfinding": "^0.4.18",
     "quickselect": "^1.0.0",