Test-Kitchen integration

@schisamo @fnichol this is obviously incomplete but should be a good illustration of our conversation today.

I'll make this a toggle-able (off by default) feature until Test-Kitchen 1.0.0.alpha is ready for a 1.0 release.

- [x] add 'test' command to berks
- [x] add test kitchen files to generators

Let's grow this list out as we come up with additional things we gotta do!

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