Specify versions of gem dependencies
Setup `appraisal` gem

Test against multiple verions of `capybara` gem. For capybara 2.4, test
against RSpec 3 and RSpec 2.
Convert specs to RSpec 3.0.4 syntax with Transpec

This conversion is done by Transpec 2.3.7 with the following command:
    transpec

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

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

For more details: https://github.com/yujinakayama/transpec#supported-conversions
Handle deprecated `treat_symbols_as_metadata_keys_with_true_values`