Updated banner

git-svn-id: https://plugins.svn.wordpress.org/instagram-feed/trunk@1008943 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updated README.txt

git-svn-id: https://plugins.svn.wordpress.org/instagram-feed/trunk@1008944 b8457f37-d9ea-0310-8a92-e5e31aec5664