Remove unused grunt libraries from package.json

package.json

@@ -31,7 +31,5 @@
         "pegjs": "~0.7.0",
         "grunt": "~0.4.0",
         "grunt-contrib-jshint": "~0.3.0",
-        "grunt-image-embed": "~0.1.3",
-        "grunt-contrib-mincss": "~0.3.2"
     }
 }