readme update

git-svn-id: https://plugins.svn.wordpress.org/atcontent/trunk@1008966 b8457f37-d9ea-0310-8a92-e5e31aec5664
readme description update

git-svn-id: https://plugins.svn.wordpress.org/atcontent/trunk@1008967 b8457f37-d9ea-0310-8a92-e5e31aec5664