kiji-scoring: SCORE-147. Add a KijiMapReduceJobBuilder implementation for running a ScoreFunction in batch.

issue: https://jira.kiji.org/browse/SCORE-147
review: https://review.kiji.org/r/1559
commit: https://github.com/kijiproject/kiji-scoring/commit/efe5ec471b922a95928c3377e2255b5489f36743