Start RSpec 3 upgrade process
Run transpec on the repo
Convert specs to RSpec 3.0.2 syntax with Transpec

This conversion is done by Transpec 2.3.1 with the following command:
    transpec -f -k oneliner,have_items,its

* 4 conversions
    from: failure_message_for_should { }
      to: failure_message { }

* 4 conversions
    from: failure_message_for_should_not { }
      to: failure_message_when_negated { }

* 1 conversion
    from: obj.stub(:message => value)
      to: allow(obj).to receive_messages(:message => value)

For more details: https://github.com/yujinakayama/transpec#supported-conversions
Fix last errors and deprecations from RSpec 3
Improve Guard configuration
Add Ruby 2.1.2 to Travis build matrix