R1:ac868f56dbdd

Maniphest mobile CSS tweaks

Summary: Fixes a few minor quirks when viewing maniphest on mobile.

Test Plan: shrink maniphest screen, easier to read.

Reviewers: epriestley

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7270