Update RSpec version to >= 2.14.0 and convert specs to new syntax

This conversion is done by Transpec 1.13.1 with the following command:
    transpec

* 14 conversions
    from: == expected
      to: eq(expected)

* 14 conversions
    from: obj.should
      to: expect(obj).to

* 14 conversions
    from: obj.should_receive(:message)
      to: expect(obj).to receive(:message)

* 1 conversion
    from: obj.should_not_receive(:message)
      to: expect(obj).not_to receive(:message)