Updating readme

git-svn-id: https://plugins.svn.wordpress.org/external-featured-image/trunk@1043435 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updating title in readme

git-svn-id: https://plugins.svn.wordpress.org/external-featured-image/trunk@1043438 b8457f37-d9ea-0310-8a92-e5e31aec5664