Update readme for 3.9

git-svn-id: https://plugins.svn.wordpress.org/post2media/trunk@895976 b8457f37-d9ea-0310-8a92-e5e31aec5664
Update readme for 3.9

git-svn-id: https://plugins.svn.wordpress.org/post2media/trunk@895977 b8457f37-d9ea-0310-8a92-e5e31aec5664