Bumped grunt-browserify version to 3.28.1 (closes snowplow#427)

Author: fblundun

package.json

@@ -5,7 +5,7 @@
     "JSON": "~1.0.0",
     "browser-cookie-lite": "~0.3.1",
     "grunt": "~0.4.2",
-    "grunt-browserify": "~1.3.0",
+    "grunt-browserify": "~4.0.1",
     "grunt-cloudfront": "^0.2.0",
     "grunt-contrib-concat": "~0.3.0",
     "grunt-lodash": "~0.3.0",