Finished testing .change() multiselect true.
And I realized something I somehow hadn't ever realized before:
`model.active()` is a horrible name for that method. When you have a
multiselect option, that word "active" doesn't make any sense, because
the program could very well make that model "deactive". So I thought
toggle might be a better word. But no, that's not good either because it
doesn't make any sense for the single select lists. I'm leaning toward
making the whole thing revolve around a verb that doesn't really have
much meaning. I'm thinking "wax" as in "wax on, wax off". That way the
model.wax() action can mean whatever we intend it to mean.