`res.writeHead(303, { Location: foreignUrl })` does not work correctly with `connect.session(...)`

[bnoguchi]

Stumbled on this while looking into a reported issue with everyauth.

The problem is that the session is not properly persisted just before the redirect. To reproduce:

1. Use the following gist
2. Go to http://localhost:3000
3. This should redirect to http://google.com
4. Then, go to http://localhost:3000/two
5. The step 2 session and step 4 session should carry the same name, but they do not -- hence, the broken assertion in the gist.

--Brian