Readme enhancements + screenshots & banner

git-svn-id: https://plugins.svn.wordpress.org/guestful-widget/trunk@896671 b8457f37-d9ea-0310-8a92-e5e31aec5664
Readme enhancements + screenshots & banner

git-svn-id: https://plugins.svn.wordpress.org/guestful-widget/trunk@896674 b8457f37-d9ea-0310-8a92-e5e31aec5664