R1:3440839c99f3

Hook Ponder to Subscriptions

Summary: Adding email aggro email aggro

Test Plan: Added some content; annoyed some coworkers.

Reviewers: epriestley, nh, vrana

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T1808

Differential Revision: https://secure.phabricator.com/D3643