Additional open options

Currently, if a user runs:
`knote -o cmput1`
and `cmput1` is not scheduled for the current day, a new note is created with the current days time stamp.

Add the following options for when a user runs open on a class which is not scheduled in the current day:
1. open previous
2. create and open new note for today
3. create and open the note for the next scheduled day of that class