added retire.js to build process

-allows security vulnerability check in used npm-dependencies and own scripts
-execute with ```grunt retire```

package.json

@@ -36,10 +36,11 @@
     "grunt-sass": "~1.1.0-beta",
     "grunt-contrib-connect": "~0.11.2",
     "grunt-autoprefixer": "~3.0.3",
+    "grunt-retire": "~0.3.10",
     "grunt-zip": "~0.17.1",
     "grunt": "~0.4.5",
     "node-sass": "~3.3.3"
   },
-  
+
   "license": "MIT"
 }