Merge pull request #27 from mongodb-js/greenkeeper-mocha-2.5.3

mocha@2.5.3 breaks build 🚨

Author: imlucas

package.json

@@ -34,7 +34,7 @@
   "devDependencies": {
     "debug": "^2.2.0",
     "eslint-config-mongodb-js": "^2.0.0",
-    "mocha": "^2.4.5",
+    "mocha": "^2.5.3",
     "mongodb-js-fmt": "^0.0.3",
     "mongodb-js-precommit": "^0.2.8",
     "mongodb-runner": "^3.3.2",