Mobile layouts for Diffusion

Summary: Implements a new mobile view thats more fullscreen, not boxed, so more space. Fixes issues with mobile tables when scrolling overflowed content.

Test Plan: Test home, branch, tags, code, file browse, graph, compare, history, readme, open revisions, owners.

Reviewers: epriestley

Reviewed By: epriestley

Spies: Korvin

Differential Revision: https://secure.phabricator.com/D18505