update readme file

git-svn-id: https://plugins.svn.wordpress.org/wr-megamenu/trunk@1012656 b8457f37-d9ea-0310-8a92-e5e31aec5664
update readme file

git-svn-id: https://plugins.svn.wordpress.org/wr-megamenu/trunk@1012660 b8457f37-d9ea-0310-8a92-e5e31aec5664