Default folders and extra information in Capybara.md

Adds the folders:
* controllers
* helpers
* models
* views

Adds a "rspec-rails_readme.txt" that points users back to rspec/rspec-rails for more information though it's probably not needed but still might be helpful since some people might not realize just how much information the base readme has, it pretty much teaches you all about rspec-rails.

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Updates Capybara.md to include information on `feature` and `scanario` in Capybara 2.