When scrolling forward a month in calendar date picker from 1/31, next chosen date should be 2/29, not 3/1.
Summary: Fixes T9295
Test Plan: Create event, open datepicker for start date, choose 1/31/2016, open datepicker again, click right button to scroll month. New suggested date should be 2/29/2016
Reviewers: chad, epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: Korvin
Maniphest Tasks: T9295
Differential Revision: https://secure.phabricator.com/D15727