add User model and secure password
add Users controller with a new action
generate integretion_test user_pages
add resources :users and show.html.erb. Also add test for user show page with factories.
define a gravatar_for helper method and add gravatar image
create app/views/shared directory with _error_messages.html.erb partial file.  This will display error messages for the signup form
add the flash variable to app/views/layouts/application.html.erb