R1:9b28724210db

Major, increase background color in blockquote

Summary: Makes quotes easier to parse visually. Major change.

Test Plan:
Quote some text.

{F282953}

{F282954}

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11678