convert remaining feature steps to RSpec 3 syntax

This conversion is done by Transpec 3.0.5 with the following command:
    transpec features/steps

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

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

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

* 2 conversions
    from: =~ /pattern/
      to: match(/pattern/)

* 2 conversions
    from: >= expected
      to: be >= expected

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