updated readme

git-svn-id: https://plugins.svn.wordpress.org/lively-chat-support/trunk@900038 b8457f37-d9ea-0310-8a92-e5e31aec5664
bump to 1.0.21

git-svn-id: https://plugins.svn.wordpress.org/lively-chat-support/trunk@900039 b8457f37-d9ea-0310-8a92-e5e31aec5664