Bump cache version

Summary:
See T1602#15.

I don't intend to land this right away, because I'm not sure I won't
need another change or two to the rendering code. Keeping it here so I
won't forget about it.

Test Plan: iiam

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T1602

Differential Revision: https://secure.phabricator.com/D3240