[WIP] Capybara2+ 対応

@mamebro/owners 
カピバラさん :up: 

* http://qa.atmarkit.co.jp/q/2680
* https://github.com/jnicklas/capybara
* http://www.andylindeman.com/2012/11/11/rspec-rails-and-capybara-2.0-what-you-need-to-know.html
* http://robots.thoughtbot.com/rspec-integration-tests-with-capybara
* https://learn.thoughtbot.com/test-driven-rails-resources/rspec_acceptance.pdf

refs: https://github.com/mamebro/mameblo/issues/124