Install Capybara for integration testing.

 * Rename spec/integration to spec/features to conform to what
   Capybara expects.
 * Require capybara/rspec in the spec_helper.
Add a simple RSpec integration test (using capybara) which tests that signing in and out works properly from the user interface.
Remove the line regarding fixtures from the RSpec configuration -- I'm using Factory Girl.
Install Poltergeist to use PhantomJS as the default javascript test driver.

  * Read the instructions here on how to install PhantomJS
      https://github.com/jonleighton/poltergeist/blob/master/README.md
  * Mark tests with :js => true to use the javascript driver, otherwise
    it'll use the default :rack_test
Merge branch 'capybara'