Finish 8.3.2: Created Cucumber Tests

1.  Used git mv to rename the spec/requests folder to spec/features.  See discussion at
    http://www.andylindeman.com/2012/11/11/rspec-rails-and-capybara-2.0-what-you-need-to-know.html
    for more information.
2.  Added cucumber-rails and database_cleaner gems to Gemfile
3.  Created cucumber signing_in.feature and authentication_steps.rb files, with successful tests.