version 3.3.1

git-svn-id: https://plugins.svn.wordpress.org/printfriendly/trunk@758404 b8457f37-d9ea-0310-8a92-e5e31aec5664
minor readme update

git-svn-id: https://plugins.svn.wordpress.org/printfriendly/trunk@758410 b8457f37-d9ea-0310-8a92-e5e31aec5664