Make checkpoints before hard wrapping

[djpaterson]

There is an issue with how Wraptor interacts with Atom's history mechanism which means that if I type a block of text that is then hard wrapped, the undo often undoes the hard wrapping rather than the actual typing (which then causes a loop of undo/redo the hard wrap)

STEPS TO REPRODUCE:

1. Create a new text file
2. Exceed the preferredLineLength variable (for testing I used "this is a long sentence that will need to hard wrap due to exceeding 80 in the current workspace"
3. Wait for hard wrap
4. Undo

Expected Outcome
The typing will be undone

Actual Outcome
The hard wrap will be undone with the text remaining - if I don't immediately press undo again, the hard wrap takes effect again, meaning no undo actually happens.

I don't know what the best way to go about solving this problem is - I'm not really convinced as to whether hard wrap should contribute to the history of the editor, but that is quite possibly an internal mechanism. I think either wraptor should recognise if a wrap has been undone and leave the line as it is (perhaps someone wants a line not wrapped) or it should make use of the createCheckpoint()/revertToCheckpoint() methods of the editor to be able to undo the typing instead of just the wrapping.