R1:2e1c7da1bfe5

Clean up some Conpherence header CSS

Summary: Darkens the topic, adds fun colors to action icons.

Test Plan: Hover over new action icons. See darker topic text.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D16556