compatibility readme

git-svn-id: https://plugins.svn.wordpress.org/facebook-like-and-send/trunk@978517 b8457f37-d9ea-0310-8a92-e5e31aec5664
compatibility readme

git-svn-id: https://plugins.svn.wordpress.org/facebook-like-and-send/trunk@978561 b8457f37-d9ea-0310-8a92-e5e31aec5664