Add scenarios with Rule keyword

[aslakhellesoy]

We need a few feature files under features/docs that use the new Rule keyword.

In particular, we should verify that the pretty formatter can render it. I can't remember if it renders the Rule lines, and if it doesn't, it's fine (ref cucumber/common#757)

[vincent-psarga]

I've added two new features here:

• e12075a
• 44509e0

Although, I'm not convinced by the examples. Is there some doc I could as descriptions for those features ?
From the docs:

The purpose of the Rule keyword is to represent one business rule that should be implemented. It provides additional information for a feature. A Rule is used to group together several scenarios that belong to this business rule. A Rule should contain one or more scenarios that illustrate the particular rule.

Would that be enough ? any idea @aslak @mattwynne @sebrose ?

[aslakhellesoy]

As long as these feature files are only used to validate/test the syntax and not provide an example of good use, I think these are fine!

[vincent-psarga]

Ok, works for me :)