README.md upgrade
readme.txt upgrade

git-svn-id: https://plugins.svn.wordpress.org/a-simple-twitter-widget/trunk@749852 b8457f37-d9ea-0310-8a92-e5e31aec5664
readme.txt update
README.md update

git-svn-id: https://plugins.svn.wordpress.org/a-simple-twitter-widget/trunk@749853 b8457f37-d9ea-0310-8a92-e5e31aec5664