kiji-phonebook: PHONE-14. Update classes to use the platform bridge.

issue: https://jira.kiji.org/browse/PHONE-14
review: https://review.kiji.org/r/1829
commit: https://github.com/kijiproject/kiji-phonebook/commit/56d9e5c01ca6e5befb682a80e5c3e78fa3ee7ff3