Update test script in package.json to run tests

The `test` script in `package.json` was just a dummy. But we provide
proper tests by running `grunt test`.

This patch updates `package.json` to have a proper `test` script.

Author: huerlisi

package.json

@@ -44,7 +44,7 @@
     "matchdep": "0.3.0"
   },
   "scripts": {
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test": "grunt test"
   },
   "repository": {
     "type": "git",