Summary:
This diff removes the timeout transition group from the sheet-toolbar, which was causing toolbar items to fade when columns were opened / closed and they were moved from column to column.
Instead, I'm just animating the message toolbar items, which are one of the few sets of toolbar items that really should fade, and do so as an entire set.
I've also renamed the "sheet-toolbar" animation to "opacity-125ms". I think it'd be cool to create a standard set of these animations, but I didn't see any others it would make sense to create generic names for yet. (The others have weird timings or are bound up inside packages).
Resolves Github #90
Test Plan: No new tests
Reviewers: evan
Reviewed By: evan
Differential Revision: https://phab.nylas.com/D2159
f7c6ae0774