chore(package): update mocha to version 3.2.0

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -51,7 +51,7 @@
     "nan": "^2.4.0"
   },
   "devDependencies": {
-    "mocha": "~3.0.2",
+    "mocha": "~3.2.0",
     "chai": "~3.5.0",
     "grunt": "~1.0.1",
     "grunt-mocha-test": "~0.13.0",