Change to readme.txt

git-svn-id: https://plugins.svn.wordpress.org/wp-symposium/trunk@905936 b8457f37-d9ea-0310-8a92-e5e31aec5664
Removed old screenshots

git-svn-id: https://plugins.svn.wordpress.org/wp-symposium/trunk@905940 b8457f37-d9ea-0310-8a92-e5e31aec5664