Updated readme and screenshots

git-svn-id: https://plugins.svn.wordpress.org/webmaster-user-role/trunk@970209 b8457f37-d9ea-0310-8a92-e5e31aec5664
fix readme and screenshots

git-svn-id: https://plugins.svn.wordpress.org/webmaster-user-role/trunk@970212 b8457f37-d9ea-0310-8a92-e5e31aec5664