Bump RSpec to ~> 2.14.0 and convert expect syntax with transpec

This conversion is done by Transpec 1.13.1 with the following command:
    transpec

* 1291 conversions
    from: obj.should
      to: expect(obj).to

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

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

* 37 conversions
    from: lambda { }.should
      to: expect { }.to

* 19 conversions
    from: lambda { }.should_not
      to: expect { }.not_to

* 9 conversions
    from: =~ [1, 2]
      to: match_array([1, 2])

* 1 conversion
    from: =~ /pattern/
      to: match(/pattern/)

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