readme and/or setup guide update

git-svn-id: https://plugins.svn.wordpress.org/nextgen-facebook/trunk@943892 b8457f37-d9ea-0310-8a92-e5e31aec5664
v7.5.5

git-svn-id: https://plugins.svn.wordpress.org/nextgen-facebook/trunk@943893 b8457f37-d9ea-0310-8a92-e5e31aec5664