delete readme.txt

git-svn-id: https://plugins.svn.wordpress.org/facebook-fanbox-popup/trunk@1005465 b8457f37-d9ea-0310-8a92-e5e31aec5664
add readme.txt

git-svn-id: https://plugins.svn.wordpress.org/facebook-fanbox-popup/trunk@1005466 b8457f37-d9ea-0310-8a92-e5e31aec5664