chore(package): update grunt-contrib-uglify to version 2.0.0

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -24,7 +24,7 @@
     "grunt-cli": "^1.2.0",
     "grunt-contrib-clean": "^1.0.0",
     "grunt-contrib-concat": "^1.0.0",
-    "grunt-contrib-uglify": "^1.0.0",
+    "grunt-contrib-uglify": "^2.0.0",
     "grunt-jsduck": "^1.0.0",
     "grunt-karma": "^1.0.0",
     "grunt-recess": "^1.0.0",