wp 4.0 support

git-svn-id: https://plugins.svn.wordpress.org/buttons-shortcode-and-widget/trunk@1012795 b8457f37-d9ea-0310-8a92-e5e31aec5664
readme update

git-svn-id: https://plugins.svn.wordpress.org/buttons-shortcode-and-widget/trunk@1012798 b8457f37-d9ea-0310-8a92-e5e31aec5664