update readme file

git-svn-id: https://plugins.svn.wordpress.org/wr-pagebuilder/trunk@1000386 b8457f37-d9ea-0310-8a92-e5e31aec5664
update readme file

git-svn-id: https://plugins.svn.wordpress.org/wr-pagebuilder/trunk@1000388 b8457f37-d9ea-0310-8a92-e5e31aec5664