Iss827

I need some help with the tests.  I've added MkCommitsTest and RtCommitsTest, but they are ignored.  The RtCommitsTest requires some knowledge of the underlying test framework which I don't have.  Likewise, the MkCommitsTest is failing because there's something else going on which I'm not familiar with.  Considering the scope of this issue (it did not take 30 minutes), I could use a hand with completing this.
You didn't implement `MkCommits.create()` yet, so this will definitely fail (with `UnsupportedOperationException`). It's all right if you think it takes too much time, don't implement it yet and leave a puzzle behind. See http://www.xdsd.org/2009/03/04/pdd.html