Provide post url in success email

git-svn-id: https://plugins.svn.wordpress.org/postie/trunk@1011691 b8457f37-d9ea-0310-8a92-e5e31aec5664
releasing 1.6.4

git-svn-id: https://plugins.svn.wordpress.org/postie/trunk@1011696 b8457f37-d9ea-0310-8a92-e5e31aec5664