chore(package): update grunt-contrib-cssmin to version 2.2.1

Author: greenkeeper[bot]

package.json

@@ -23,7 +23,7 @@
     "grunt-concurrent": "2.3.1",
     "grunt-contrib-clean": "1.1.0",
     "grunt-contrib-copy": "1.0.0",
-    "grunt-contrib-cssmin": "2.2.0",
+    "grunt-contrib-cssmin": "2.2.1",
     "grunt-contrib-jshint": "1.1.0",
     "grunt-contrib-watch": "1.0.0",
     "grunt-postcss": "0.8.0",