1-  bundle update

2- Modificado  enviroments/development.rb por error el ejecutar el comando del tutorial:

rails generate scaffold User name:string email:string

El error es:
...rails_projects/demo_app/config/environments/development.rb:1:in `<top (required)>': undefined method `configure' for #<DemoApp::Application:0x007fdcea90ae10> (NoMethodError)

Ver:
http://stackoverflow.com/questions/23388205/rails-generate-scaffold-error