ensure :quit and :quit! take no arguments

[the-mikedavis]

I lost my train of thought and accidentally typed :q! :w 😄

Since quitting is a little destructive, I think it makes sense to fail the quit if it's not a well-formed 0-arg :quit(!).

What do you think?

[dylrich]

I think this is a good idea, particularly for :q!

[archseer]

Agree, we should check args.len() in each command. This works as a quick fix though