Fix collaborative undo correctness (fixes #2105)#2500

Merged

jhchen merged 7 commits intodevelopfrom dg-collab-undo

Feb 12, 2019

+704-489

Commits on Feb 12, 2019

update dependencies
jhchen
committed
tests pass

dgreensp
authored and
jhchen
committed
change undo/redo stacks to be arrays of simple deltas

dgreensp
authored and
jhchen
committed
don't record empty undo

dgreensp
authored and
jhchen
committed
add a test

dgreensp
authored and
jhchen
committed
remove debugging stuff

dgreensp
authored and
jhchen
committed
update quill-delta and use its invert()
jhchen
committed