kiji-bento: BENTO-73. Update REVIEWERS file.

issue: https://jira.kiji.org/browse/BENTO-73
review: https://review.kiji.org/r/1810
commit: https://github.com/kijiproject/kiji-bento/commit/c1dca5fa9d01397874b1a7880d4febf775bc7a3c