Calendar month view "today" indicator should be a blue bar across the bottom of the day cell

Summary: Ref T4392, Calendar month view "today" indicator should be a blue bar across the bottom of the day cell

Test Plan: Open month view of Calendar, today should have a blue bar across the bottom of the day cell

Reviewers: chad, epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T4392

Differential Revision: https://secure.phabricator.com/D12815