Bump to RSpec 3+
Remove deprecated option (it's always on now)
Convert specs to RSpec 3.0.3 syntax with Transpec

This conversion is done by Transpec 2.3.6 with the following command:
    transpec -b true,false -f

* 21 conversions
    from: obj.stub!(:message)
      to: allow(obj).to receive(:message)

* 17 conversions
    from: obj.should_receive(:message)
      to: expect(obj).to receive(:message)

* 15 conversions
    from: stub('something')
      to: double('something')

* 3 conversions
    from: obj.stub(:message)
      to: allow(obj).to receive(:message)

* 1 conversion
    from: obj.should_not_receive(:message)
      to: expect(obj).not_to receive(:message)

* 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
Correct RSpec matcher usage (broke under RSpec 3)
Update travis configuration (rbx-2)
Use `Encoding` constants