new readme.txt

git-svn-id: https://plugins.svn.wordpress.org/ultimate-social-media-icons/trunk@1044009 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated readme.txt

git-svn-id: https://plugins.svn.wordpress.org/ultimate-social-media-icons/trunk@1044014 b8457f37-d9ea-0310-8a92-e5e31aec5664