Unsubscribe workflow

This is my unsubscribe workflow branch, based on @maxking 's original branch. It closes #213 (closed) but it doesn't pass all its tests. Specifically, a couple of database migration tests fail, and I haven't figure out why yet. Maybe @maxking has some insight.

I'd like to get the tests passing and then do a final cleanup pass on the code. In the meantime, all other comments welcome of course.