Timeout whilst getting response's body

Hi,

I've started using treq on unstable network and I realized that there is no way to define timeout while getting response content. So sometimes I can't process request as it is hanged.

My idea to solve that is to pass request_kwargs to _Response and _BufferedResponse and collect function should look like:

def collect(response, request_kwargs, collector):
    """
    Incrementally collect the body of the response.

    This function may only be called **once** for a given response.

    :param IResponse response: The HTTP response to collect the body from.
    :param collector: A callable to be called each time data is available
        from the response body.
    :type collector: single argument callable

    :rtype: Deferred that fires with None when the entire body has been read.
    """
    if response.length == 0:
        return succeed(None)

    d = Deferred()
    response.deliverBody(_BodyCollector(d, collector))
    if request_kwargs.get('timeout'):
        delayedCall = default_reactor(request_kwargs.get('reactor')).callLater(
            request_kwargs.get('timeout'), d.cancel)

        def gotResult(result):
            if delayedCall.active():
                delayedCall.cancel()
            return result

        d.addBoth(gotResult)
    return d

Guys, can you confirm that issue makes sense?
If yes, I'll prepare more proper fix with tests.

Cheers!

Start by reading _Response, _BufferedResponse, and collect, then trace how request_kwargs and the reactor are passed into response-body handling. Confirm the timeout behavior around _BodyCollector and identify the existing test layout before adding coverage. Done means response collection can honor the request timeout and the timeout is cleaned up when collection finishes.