kiji-poms: POM-29. Add scala-reflect to the root pom.

issue: https://jira.kiji.org/browse/POM-29
review: https://review.kiji.org/r/1762
commit: https://github.com/kijiproject/kiji-poms/commit/f95269c3bafbb49d5f31cf9c5265f4249a50c389