updated readme

git-svn-id: https://plugins.svn.wordpress.org/wp-paywall/trunk@1004010 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated readme

git-svn-id: https://plugins.svn.wordpress.org/wp-paywall/trunk@1004011 b8457f37-d9ea-0310-8a92-e5e31aec5664