Add ability to not import overdue assignments.

[JOOT49]

The script will currently import way overdue assignments that may not have needed a submission.
Comparing the date with the current date and not adding should be a pretty simple fix.

Another way to fix this would be to not import tasks into todoist that have been marked as complete, this could be very difficult to implement, however.

Either method would work!

[stacksjb]

This script intentionally imports any assignment which you can submit, but has not been submitted

If it's overdue, that is not pulled into the logic, because if you can submit it, then that logic is left open. Any filtering on due date should be done in todoist.

I can certainly add some sort of calculation for this down the road but I'm not likely to do this at the moment because the simple fact that something is overdue doesn't determine whether a teacher accepts it or it has a grade. I personally have submitted blink assignments plenty of times.