add clean to package

package.json

@@ -6,10 +6,10 @@
     "grunt": "~0.4.1",
     "grunt-contrib-compass": "~0.2.0",
     "grunt-contrib-watch": "~0.4.3",
-    "grunt-contrib-uglify": "~0.2.0",
     "grunt-exec": "~0.4.2",
     "grunt-contrib-connect": "0.5.0",
     "grunt-contrib-copy": "0.4.1",
+    "grunt-contrib-clean": "0.5.0",
     "matchdep": "~0.1.2"
   }
 }