Display auditors in audit commit list

Summary: Users wonder who is actually doing all these audits.

Test Plan:
/owners/package/1/
/audit/view/packagecommits/?phid=PHID-OPKG-1

Reviewers: epriestley

Reviewed By: epriestley

CC: jungejason, aran, Korvin

Differential Revision: https://secure.phabricator.com/D3597