R1:3747a3547610

Allow mail replies to Phame Posts

Summary: Adds mail reply support to Phame Posts.

Test Plan: Comment on a post, get mail.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T9746

Differential Revision: https://secure.phabricator.com/D14454