readme update

git-svn-id: https://plugins.svn.wordpress.org/wpsso/trunk@841242 b8457f37-d9ea-0310-8a92-e5e31aec5664
1.23dev1

git-svn-id: https://plugins.svn.wordpress.org/wpsso/trunk@841244 b8457f37-d9ea-0310-8a92-e5e31aec5664
1.23dev1

git-svn-id: https://plugins.svn.wordpress.org/wpsso/trunk@841245 b8457f37-d9ea-0310-8a92-e5e31aec5664