Split run() into setup and execution

[WojciechMigda]

Hi,
would it be possible to split run() method into preparation part, which creates sending and receiving coroutines and the execution part?

Right now, with the code I am integrating your module into, I had to copy-paste some of the run() functionality into:

def ready(self, host, port, loop=None):
    self.loop = loop or asyncio.get_event_loop()
    self.sock.bind((host, port))
    self.connection_made()
    stask = self._send_periodically()
    rtask = self._recv_periodically()
    return stask, rtask

so that later I could schedule execution with some other coroutine using Nursery from aionursery. Otherwise, I was running into exceptions being thrown while my app was exiting.
Thanks.

[bashkirtsevich]

Feel free to send a pull request.