R1:d85386488bf5

Add "wide" remarkup image support for Documents

Summary: Seems to work ok, if you give `size=wide` to an image file, we blow it out a bit in DocumentPro mode.

Test Plan:
Test in Phame and Maniphest.

{F1256717}

{F1256718}

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D15840