README.md upgrade

git-svn-id: https://plugins.svn.wordpress.org/a-simple-twitter-widget/trunk@749838 b8457f37-d9ea-0310-8a92-e5e31aec5664
README.md upgrade

git-svn-id: https://plugins.svn.wordpress.org/a-simple-twitter-widget/trunk@749839 b8457f37-d9ea-0310-8a92-e5e31aec5664
README.md upgrade

git-svn-id: https://plugins.svn.wordpress.org/a-simple-twitter-widget/trunk@749843 b8457f37-d9ea-0310-8a92-e5e31aec5664
readme.txt add

git-svn-id: https://plugins.svn.wordpress.org/a-simple-twitter-widget/trunk@749844 b8457f37-d9ea-0310-8a92-e5e31aec5664