Conpherence - tweak calendar widget

Summary: this does a few things. Fixes T3253. Including the Sunday -> Saturday list view part. Cleans up the display when there are no events, getting rid of this spacer thing. Also fixes Calendar CSS for device-tablet where we had a 2px gap on the calendar from the header.

Test Plan: played with calendar widget a bunch

Reviewers: epriestley, chad

Reviewed By: chad

CC: aran, Korvin

Maniphest Tasks: T3253

Differential Revision: https://secure.phabricator.com/D6102