Eliminated complex List Table query and replaced it with get_users(), fixed search and sorting.

git-svn-id: https://plugins.svn.wordpress.org/email-users/trunk@778448 b8457f37-d9ea-0310-8a92-e5e31aec5664
Removed old complex query method.

git-svn-id: https://plugins.svn.wordpress.org/email-users/trunk@778449 b8457f37-d9ea-0310-8a92-e5e31aec5664