http: Refactor for streams2

Because of some of the peculiarities of http, this has a bit of special
magic to handle cases where the IncomingMessage would wait forever in a
paused state.

In the server, if you do not begin consuming the request body by the
time the response emits 'finish', then it will be flushed out.

In the client, if you do not add a 'response' handler onto the request,
then the response stream will be flushed out.