R1:ce0cb115ca2a

Add Hero Image to Phame Post

Summary: Adds a headerimage and lets you set it on posts for added reverence. Is that a word?

Test Plan:
Add an image, see an image.

{F1923010}

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D16873