updated readme.txt file for supported themes

git-svn-id: https://plugins.svn.wordpress.org/facebook-pagelike-widget/trunk@960474 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated readme.txt file for supported themes

git-svn-id: https://plugins.svn.wordpress.org/facebook-pagelike-widget/trunk@960475 b8457f37-d9ea-0310-8a92-e5e31aec5664