Summary:
fix(scrollbars): overflow-y, not overflow
fix(participants): Overflow not set correctly on participants
fix(thread-list): Don't show reply or fw icon for unsent drafts
Remove bad code for updating sidebar drafts
Mark as read in MessageStore so that receiving new messages while viewing a thread re-marks it as read
Don't show messages I send with the "Reply" icon
Test Plan: Run tests
Reviewers: evan
Reviewed By: evan
Differential Revision: https://review.inboxapp.com/D1418