R1:ce8799176e8b

Add author field to image macro display

Summary:
this is a request from Facebook:
> someone has added macros for common words like 'push', 'lgtm'.
> We want to let he image macro page at least attribute to an owner so
> that we can publicly shame whoever added the 800px 'clowntown' macro.

Test Plan:
test macros with/without author (all macro should have
author. This is just to be safe).

Reviewers: epriestley, nh

Reviewed By: epriestley

CC: hwang, aran, arice, jungejason, epriestley

Differential…