Convert specs to RSpec 3.1.4 syntax with Transpec

I noticed RSpec deprecation warnings so I converted the the specs from the "should" syntax to the "expect" syntax preferred by RSpec. This conversion was done using the Transpec gem. Full details can be found in the detailed commit message below generated by the gem. All tests pass before and after the conversion.

This conversion is done by Transpec 2.3.3 with the following command:
    transpec

* 217 conversions
    from: obj.should
      to: expect(obj).to

* 207 conversions
    from: == expected
      to: eq(expected)

* 8 conversions
    from: obj.should_not
      to: expect(obj).not_to

For more details: https://github.com/yujinakayama/transpec#supported-conversions