readme update

git-svn-id: https://plugins.svn.wordpress.org/feed-them-social/trunk@967011 b8457f37-d9ea-0310-8a92-e5e31aec5664
update 1.5.2

git-svn-id: https://plugins.svn.wordpress.org/feed-them-social/trunk@967013 b8457f37-d9ea-0310-8a92-e5e31aec5664