KIJIMR-64. Sets start and limit keys on the mapreduce job

This is not a full solution to KIJIMR-64, but it does address passing the start and limit keys into the mapreduce job.  I added a new integration test.  If you have suggestions for how you would like to see the `getSplits` method be tested, I am all ears.  It seems like using mocks might be the best way to go, so that I could test many different edge cases.