KIJIMR-287. Upgrade mrunit and make it a test dependency.
KIJIMR-287. Upgrade mrunit and make it a test dependency.

MRUnit was a compile time dependency making it get pulled into other projects'
classpath which is not desirable in case of classpath issues.

Review: https://review.kiji.org/r/1961/
Reviewer: taton

iafek/kiji-mapreduce,kijiproject/kiji-mapreduce,kijiproject/kiji-mapreduce,iafek/kiji-mapreduce,kijiproject/kiji-mapreduce