Feature request: Send to firebase Topic

[jsmolina]

I think this quite simple but also good library is missing just 'send to topic' implementation. Something simple like this could work:

result = dict(
            message_id=self.message_id,
            to=self.device_token or  '/topics/{0}'.format(self.topic_name),
        )

Of course, current implementation allows reusing device_token and just sending the /topics with it, but this way will be more simple

[jfgaudreault-p]

+1