Create a Rails 4.1 app

* Update new routes line.
* Remove explicit spring binstub creation as Rails now does it for us.
* Use `Rails.application` consistently.
* Use new `config/secrets.yml` convention with existing
  `SECRET_KEY_BASE` environment variable setup.
* Rails 4 prefers Ruby 2.0 and requires 1.9.3 or newer.
  http://guides.rubyonrails.org/upgrading_ruby_on_rails.html