kiji-bento: BENTO-59. Add KijiScoringServer to the bento box.

issue: https://jira.kiji.org/browse/BENTO-59
review: https://review.kiji.org/r/1315
commit: https://github.com/kijiproject/kiji-bento/commit/9ef523b87de10313e42a8bcf8afe18fded99945e