add "author" information to conduit call

Summary: 'cuz we need it in arcanist for T479 to commit as author

Test Plan: verified the return value was correct in conduit

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T479

Differential Revision: https://secure.phabricator.com/D3917