4.0 readme update

git-svn-id: https://plugins.svn.wordpress.org/page-links-single-page-option/trunk@980908 b8457f37-d9ea-0310-8a92-e5e31aec5664
4.0 readme update

git-svn-id: https://plugins.svn.wordpress.org/page-links-single-page-option/trunk@980910 b8457f37-d9ea-0310-8a92-e5e31aec5664