R1:3b5f0276d1f6

Fix issue where 'changeType' is not marshalled across Conduit

Summary: This leads to the "Change" column always showing "Unknown".

Test Plan: "Change" column now shows, e.g., "Contents Modified".

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7041