fixes tests and deprecation warning for pyramid versions >= 1.5 

Hi there,
we are using pyramid 1.5 and i noticed a deprecation warning about unauthenticated_userid whenever i started the server.
i've searched around a bit and noticed that pyramid >= 1.5 has deprecated unauthenticated_userid(request) in favor of request.unauthenticated_userid.
My patch basically only checks if the request supports unauthenticated_userid and if so uses that and if not falls back to the old way of doing things.
Then i noticed that the test suite fails for pyramid 1.5 and fixed that by switching do the DummyRequest object provided by the pyramid framework
cheers,
alexander