chore(package): update mocha to version 3.1.2

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -31,7 +31,7 @@
   "devDependencies": {
     "chai": "3.3.0",
     "coffee-script": "1.10.0",
-    "mocha": "2.5.3"
+    "mocha": "3.1.2"
   },
   "engines": {
     "node": "~0.10.26"