Additional setup required:

1. Verify that default settings in config/initializers/secure_password.rb
   are suitable for your purposes.

2. Enable secure_password modules by adding all of them or just the ones you
   want to your User model. See the README for instructions.

3. Perform a database migration to create the PreviousPasswords table. This
   step is not necessary if you only intend to enable the password content
   module (password_has_required_content). See the README for instructions.

4. Add flash messages in app/views/layouts/application.html.erb.
   For example:

     <p class="notice"><%= notice %></p>
     <p class="alert"><%= alert %></p>