update stylesheet for shortcode


git-svn-id: https://plugins.svn.wordpress.org/simple-instagram-widget/trunk@951041 b8457f37-d9ea-0310-8a92-e5e31aec5664
update readme

git-svn-id: https://plugins.svn.wordpress.org/simple-instagram-widget/trunk@951042 b8457f37-d9ea-0310-8a92-e5e31aec5664