Use checkpoints instead of open-ended transactions
Merge pull request #448 from atom/mb-use-checkpoints

Use checkpoints instead of open-ended transactions
Prepare 0.19.1 release
:lipstick:
Remove insert mode undo workaround

It is no longer necessary, now that insert mode groups undo entries
using checkpoints instead of open-ended transactions
Don't use WorkspaceView in FocusAction and subclasses
Don't use WorkspaceView in main package spec