Use grunt-contrib-mincss ~0.3.1

Was at ~0.3.2, but doesn't seem to have been released properly.

package.json

@@ -22,6 +22,6 @@
 		"mustache" : "~0.4.0"
 	},
 	"devDependencies": {
-		"grunt-contrib-mincss": "~0.3.2"
+		"grunt-contrib-mincss": "~0.3.1"
 	}
 }