Handler to stream data to the request.
t() :: %HTTProt.Request.Stream{request: HTTProt.Request.t, socket: Socket.Stream.t}
close(t) :: :ok | {:error, term}
close!(t) :: :ok | no_return
new(HTTProt.Request.t) :: t
write(t, iodata) :: :ok | {:error, term}
write!(t, iodata) :: :ok | no_return