Don't mangle the options object in res.cookie

Make a copy of the cookie options before mutating it to pass to
cookie.serialize. This prevents unexpected things from happening when
we try to use the same options object multiple times.

Also add a test to verify that the options object does not change
after a request is made.
update connect
Release 3.0.6
Make vhost example work on localhost

Since req.subdomains doesn't return the last two parts of the domain,
subdomains of localhost won't show up in the array. Parse the host
directly to get the first part instead.