minify js files using gruntjs and uglifyjs


git-svn-id: https://plugins.svn.wordpress.org/post-highlights/trunk@823333 b8457f37-d9ea-0310-8a92-e5e31aec5664
release version 2.5


git-svn-id: https://plugins.svn.wordpress.org/post-highlights/trunk@823334 b8457f37-d9ea-0310-8a92-e5e31aec5664