R1:7899068cec2c

Minor Conpherence CSS tweaks

Summary:
- Elastic scrolling in message view
- Form now 100% wide in mobile

Test Plan: Mobile iOS, Chrome

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5665