readme update

git-svn-id: https://plugins.svn.wordpress.org/wpsso/trunk@903519 b8457f37-d9ea-0310-8a92-e5e31aec5664
v2.4.7

git-svn-id: https://plugins.svn.wordpress.org/wpsso/trunk@903521 b8457f37-d9ea-0310-8a92-e5e31aec5664