Possibly fix memes in email

Summary:
Depends on D19201. Ref T13101. This likely produces relatively stable-ish image references for email.

They currently TTL after 30 days but this makes the jokes more exclusive and special so it's a feature, not a bug.

Test Plan: I'm just going to test this in production because I'm a ninja superstar developer.

Maniphest Tasks: T13101

Differential Revision: https://secure.phabricator.com/D19203