R1:3ceaad1aa8b7

Add basic email support to Pholio

Summary: These emails aren't yet useful, but thread/multiplex/etc correctly.

Test Plan: Got some Pholio emails.

Reviewers: btrahan, chad

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2097

Differential Revision: https://secure.phabricator.com/D3842