fix(package): update grunt-contrib-cssmin to version 3.0.0

Closes #15

Author: greenkeeper[bot]

package.json

@@ -10,7 +10,7 @@
     "grunt-contrib-coffee": "~1.0.0",
     "grunt-contrib-concat": "~1.0.1",
     "grunt-contrib-copy": "~1.0.0",
-    "grunt-contrib-cssmin": "~2.0.0",
+    "grunt-contrib-cssmin": "~3.0.0",
     "grunt-contrib-jst": "~1.0.0",
     "grunt-contrib-less": "1.4.1",
     "grunt-contrib-uglify": "~2.1.0",