Attribute revision promotion from "Draft" to "Needs Review" to the author

Summary:
Ref T2543. When Harbormaster finishes builds and promotes a draft revision to review, we currently publish "Harbormaster requested review of...".

Instead, attribute this action to the author, since that's more natural and more useful.

Test Plan: Promoted a diff locally, saw it attributed to me rather than Harbormaster.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T2543

Differential Revision: https://secure.phabricator.com/D18730