Add a wrapper div for mobile tables.

Summary: This wraps tables in a scrollable area when viewports are too narrow for the content.

Test Plan: Tested table layout in Chrome and iOS. Config was easiest table to test on mobile.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4586