Build: Introduce npm script for cleanup

Author: gibson042

README.md

@@ -40,7 +40,7 @@ cd $cdn
 git push -f
 cd -
 
-rm -rf __release/
+npm run clean
 node release.js --remote=$project
 ```
 

package.json

@@ -12,7 +12,8 @@
     "grunt-contrib-jshint": "~0.7.2"
   },
   "scripts": {
-    "test": "grunt"
+    "test": "grunt",
+    "clean": "rm -rf __release/"
   },
   "repository": "jquery/jquery-release",
   "license": "MIT"