remove gems version dependency
Convert specs to RSpec 3.0.0 syntax with Transpec

This conversion is done by Transpec 2.2.1 with the following command:
    transpec

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

* 11 conversions
    from: be_true
      to: be_truthy

* 8 conversions
    from: == expected
      to: eq(expected)

* 4 conversions
    from: be_false
      to: be_falsey

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

For more details: https://github.com/yujinakayama/transpec#supported-conversions
Merge branch 'rspec3'