update read me with warning about no admin panel 

git-svn-id: https://plugins.svn.wordpress.org/ridiculously-responsive-social-sharing-buttons/trunk@925408 b8457f37-d9ea-0310-8a92-e5e31aec5664
clarify readme.txt

git-svn-id: https://plugins.svn.wordpress.org/ridiculously-responsive-social-sharing-buttons/trunk@925409 b8457f37-d9ea-0310-8a92-e5e31aec5664