Bump RSpec to 3.0
Convert specs to RSpec 3.0.2 syntax with Transpec

This conversion is done by Transpec 2.2.4 with the following command:
    transpec

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

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

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

* 1 conversion
    from: be_false
      to: be_falsey

* 1 conversion
    from: be_true
      to: be_truthy

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