Cancel non-happy-path stream.

[coolaj86]

request({ ..., stream: ws }).then(mustOk);

There should be a way for the mustOk function to cancel ws.

[coolaj86]

Possibly add resp.stream.unpipe()?

            if (opts.stream) {
                resp.stream = setupPipe(resp, opts);
                //resp.stream.stream = opts.stream;
                resp.stream.unpipe = function () {
                    resp.unpipe(opts.stream);
                };

            // ...

            }