Convert specs to RSpec 3.1.5 syntax with Transpec

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

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

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

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

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