Build: Use a fixed Grunt version

Author: mgol

package.json

@@ -21,7 +21,7 @@
   ],
   "dependencies": {
     "async": "3.2.0",
-    "grunt": "^1.3.0",
+    "grunt": "1.3.0",
     "grunt-cli": "1.3.2",
     "grunt-jquery-content": "3.0.3"
   }