readme update

git-svn-id: https://plugins.svn.wordpress.org/nextgen-facebook/trunk@800105 b8457f37-d9ea-0310-8a92-e5e31aec5664
improved reset_metabox_prefs() option

git-svn-id: https://plugins.svn.wordpress.org/nextgen-facebook/trunk@800106 b8457f37-d9ea-0310-8a92-e5e31aec5664