Add Devise-enabled User
Add token authentication token to User
Add scaffolded PrivatePost

This model was generated by:
`rails generate scaffold PrivatePost title:string body:text \
 --test-framework rspec \
 --fixture-replacement factory_girl`

See https://github.com/gonzalo-bulnes/simple_token_authentication/blob/\
    fix-authentication-token-not-renewed-after-password-change/features/\
    step_definitions/dummy_app_steps.rb#L127
Ensure `authenticate_user!` and `sign_in` raise an exception
Ensure User `acts_as_token_authenticatable`
Ensure PrivatePostsController acts as token auth. handler for User
Add PrivatePostController decorator
Silence the failing PrivatePostsController examples

These examples fail because of token authentication, which is not
the topic of interest right now.

See https://github.com/gonzalo-bulnes/simple_token_authentication/blob/\
    fix-authentication-token-not-renewed-after-password-change/\
    features/step_definitions/dummy_app_steps.rb#L383