Update Conpherence CSS

Summary:
Updates Conpherence CSS for mostly responsive design. Notably:
- Clipped nav 20px
- Clipped widgets 40px
- Tested tablet and phone layouts
- Phone layout mostly done.
- Bouncy webkit scroll areas.

Still more work to do, but I think it should be easy now for Bob to lay in the rest of mobile. It probably doesn't need to render the menu and conversation in the widget area, as I think we can now credibly position: fix it in mobile. Not completely sold on tablet layout, but it's still better than current.

Test Plan: Tested layouts on iPhone and iPad simulator.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2421

Differential Revision: https://secure.phabricator.com/D5442