Add a show method for User, add route and view. Also insert debug params in development.
Add a helper for the users' gravatars and use it in the users show view.
Update show view and styles.
Define a User create method, add model validation and styles.
Add integration test for not saving an invalid user.
Add a flash after a successfully-created user and loop over the flash hash in the layout.
Add integration test to check for a valid user signup and redirect.