Exclude grunt copy from installation.

Removes the copy step from the grunt tasks that are run on installation.
These tasks fail if the project is not built yet, and are unnecessary,
as the maven build will copy the files regardless of grunt.

src/main/webapp/package.json

@@ -26,7 +26,7 @@
     "pixrem": "^3.0.2"
   },
   "scripts": {
-    "postinstall": "bower install && grunt",
+    "postinstall": "bower install && grunt process",
     "docs": "grunt docs"
   }
 }