Summary: Removes header gradient images for flat, CSS controlled colors. I didn't convert the "pony" colors over, going with few options for easier theme-ability.
Test Plan:
Test each color choice.
{F1063828}
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D15052
550793f9a4