kiji-mapreduce-lib: EXP-420. Update to scala 2.10

issue: https://jira.kiji.org/browse/EXP-420
review: https://review.kiji.org/r/1699
commit: https://github.com/kijiproject/kiji-mapreduce-lib/commit/738e00d6f66ae79d08d62409671e79c5453a67c2