added 3.9 compatibility in readme

git-svn-id: https://plugins.svn.wordpress.org/lp-content-manager/trunk@894811 b8457f37-d9ea-0310-8a92-e5e31aec5664
2.0.1

git-svn-id: https://plugins.svn.wordpress.org/lp-content-manager/trunk@895221 b8457f37-d9ea-0310-8a92-e5e31aec5664