Add is_admin to notification messages

git-svn-id: https://plugins.svn.wordpress.org/double-opt-in-for-download/branches/working@794243 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updated Wordpress version to 3.7.1

git-svn-id: https://plugins.svn.wordpress.org/double-opt-in-for-download/branches/working@795610 b8457f37-d9ea-0310-8a92-e5e31aec5664