prevent options object from being passed to qs as delim

As far as I can tell, versions of `qs` prior to 1.0.0, there has never
been an options object parameter to `qs.parse`, however connect has
supported passing such an object to parse since a73dd2bc0e. In `qs` 1.2.0,
which the 2.x branch of connect is currently dependent on, parse takes 3
parameters, and if the second parameter is not a number, it is treated
as the third parameter, the delimiter. As a result, you'll end up with
the object as the delimiter, which isn't good.

What I've done here is remove the ability to pass the options object to
`qs.parse`. If it's there, it will just be ignored. It was never actually
being used anyway.

Support for the new call signature could be added, but I'm guessing
that's more of a 3.x thing.