Re-added RSpec formatter.
Update gems.
Add transpec to Gemfile.
Convert specs to RSpec 2.14.6 syntax with Transpec

This conversion is done by Transpec 2.3.6 with the following command:
    transpec

* 11 conversions
    from: obj.should
      to: expect(obj).to

* 2 conversions
    from: obj.should_not
      to: expect(obj).not_to

For more details: https://github.com/yujinakayama/transpec#supported-conversions