chore(package): update grunt-contrib-uglify to version 4.0.1

Closes #4

Author: greenkeeper[bot]

package.json

@@ -28,7 +28,7 @@
     "grunt": "^1.0.1",
     "grunt-contrib-copy": "~1.0.0",
     "grunt-contrib-jshint": "~1.1.0",
-    "grunt-contrib-uglify": "~2.3.0",
+    "grunt-contrib-uglify": "~4.0.1",
     "grunt-contrib-watch": "^1.0.0",
     "grunt-jsdoc": "^2.1.0",
     "grunt-jsdoc-plugin": "~0.1.4",