add mocha as a devDependency since peerDependencies are no longer installed

Author: magalhas

package.json

@@ -49,6 +49,7 @@
     "grunt-mocha-test": "~0.12.4",
     "grunt-shell": "~1.1.1",
     "grunt-update-submodules": "~0.4.1",
+    "mocha": "^2.4.5",
     "q": "^1.2.0",
     "xyz": "^0.5.0"
   },