aggiunto il modulo 'time-grunt' necessario al task 'serve'

package.json

@@ -16,5 +16,8 @@
     "grunt-contrib-watch": "^0.6.1",
     "grunt-newer": "^1.1.1",
     "grunt-wiredep": "^2.0.0"
+  },
+  "dependencies": {
+    "time-grunt": "^1.2.1"
   }
 }