Summary: First pass here, still needs some UI work (maybe? tablets?). Getting it out to see if implementation is corrrect.
Test Plan: Shrink Maniphest task on Chrome, see new UI. Toggle menu. Test on iOS.
Reviewers: epriestley, btrahan
Reviewed By: epriestley
CC: aran, Korvin
Differential Revision: https://secure.phabricator.com/D5631
