added grunt plugins

package.json

@@ -8,11 +8,14 @@
   "devDependencies": {
     "R2": "^1.4.3",
     "grunt": "~0.4.5",
+    "grunt-contrib-clean": "^0.6.0",
     "grunt-contrib-cssmin": "^0.12.2",
+    "grunt-contrib-jshint": "^0.11.2",
     "grunt-contrib-less": "^0.12.0",
     "grunt-contrib-uglify": "^0.7.0",
     "grunt-contrib-watch": "~0.6.1",
     "grunt-cssjanus": "^0.2.4",
+    "grunt-image": "^1.0.5",
     "grunt-includes": "^0.4.5"
   }
 }