chore(package): update mocha to version 2.4.2

http://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -30,7 +30,7 @@
     "coveralls": "^2.11.4",
     "eslint-config-mongodb-js": "^1.0.5",
     "istanbul": "^0.4.0",
-    "mocha": "~2.3.3",
+    "mocha": "~2.4.2",
     "mongodb-js-fmt": "0.0.3",
     "mongodb-js-precommit": "^0.2.8",
     "pre-commit": "^1.1.2",