Badge request: Kiln review

[neal-nankivell]

I would like to add support for badge that summarises the status of a kiln review.

Example badges:

Example url:
https://img.shields.io/fogcreek/kiln/review/K12345.svg

This would be using the kiln review api 2.0

What I'm most unsure about is that because this is a service behind a paywall, I don't think I would be able to add service tests or live examples to the try.html. So I'm also a little unsure if shields accepts support for services like this.

I'm interested in submitting a pull request for this but just want to make this feature request is all good first.