kiji-scoring: SCORE-150. Correct documentation in KjiiBatchScoreTool

issue: https://jira.kiji.org/browse/SCORE-150
review: https://review.kiji.org/r/1602
commit: https://github.com/kijiproject/kiji-scoring/commit/ba1ebc6af571d3615f28266e2970d78500ed1d1e