Improve logging

[verhovensky]

Would be great if we add some configured logging on event send. To be able to see logs from Django itself if we do not use Pushpin of FanOut services For example here:

    def add_to_queues(self, channel, event):
        self.lock.acquire()
        try:
            wake = []
            listeners = self.listeners_by_channel.get(channel, set())
            for listener in listeners:
                items = listener.channel_items.get(channel)
                if items is None:
                    items = []
                    listener.channel_items[channel] = items
                if len(items) < MAX_PENDING:
                    items.append(event)  # here
                    wake.append(listener)
                else:
                    listener.overflow = True
            for listener in wake:
                listener.wake_threadsafe()
        finally:
            self.lock.release()

Thoughts?

[jkarneges]

Good idea. I've added some log messages.