NeXTless

This version releases support for "final" middleware that doesn't require a "next" handler. It could be ignored before using the _ Swift syntax, but now it isn't required at all.

Before (still works):

app.get { req, res, _ in res.send("Hi!") }

New:

app.get { req, res in res.send("Hi!") }

Two chars saved, nice! (and higher compat w/ Express, which due to JavaScript semantics doesn't require any parameter to be declared).

Important: Such "final" middleware must end the response that is passed in!