Pluralized the users controller name.
Testing for uniqueness of email.  Also seeding database with a single user.
NOTE: I seriously considered Ryan Bates' railscast on polymorphic associations for stateful users.
See http://railscasts.com/episodes/394-sti-and-polymorphic-associations
Ultimately decided that it was more robust of a solution than I needed for the task at hand.
Flushing out the controller and views.
UsersController is tested and working for admins.
Tested UsersController for non-admin users.
Added a logout button.  Plus an alert comes up for non-admin attempting to access admin actions.