add notes endpoint

[bodymindarts]

I was messing around with the wlist tool a little bit to get to know the API and decided to implement this issue.

To remain consistent two more command line options needed to be added. I chose -k for :task_id and -n for :content.

Commands added:

wlist list:notes -i <list-id>
wlist task:notes -i <task-id>
wlist note -i <note-id>
wlist note:create -k <task-id> -n <content>
wlist note:update -i <note-id> -r <revision> -n <content>
wlist note:delete -i <note-id> -r <revision>

closes #6