enhance readme

git-svn-id: https://plugins.svn.wordpress.org/authenticator/trunk@939099 b8457f37-d9ea-0310-8a92-e5e31aec5664
enhance readme

git-svn-id: https://plugins.svn.wordpress.org/authenticator/trunk@939101 b8457f37-d9ea-0310-8a92-e5e31aec5664