This should have been done a *long* time ago, back when I initially
added Websocket support. This is the first part of two in improving
loop handler support with regards to socket closure.
Reason may include: {normal, shutdown} for the most normal shutdown,
{normal, timeout} for a loop handler timeout shutdown, or {error, _}
if an error occured.
Introduces 3 low level functions and updates the existing higher
levels functions. The new primitives are has_body/1, body_length/1
and stream_body/1. In addition to that, a helper function
init_stream/4 has been added.
Streaming a body implies to decode the Transfer-Encoding and
Content-Encoding used for the body. By default, Cowboy will try
to figure out what was used and decode them properly. You can
override this if you want to disable this behavior or simply
support more encodings by calling the init_stream/4 function
before you start streaming the body.
