Summary: Adds a new header layout for Phame Blog. Subtitles now also.
Test Plan:
With Image, With Subtitle, Without Image, Without Subtitle. Mobile, Tablet, Desktop.
{F1691506}
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D16147
