Django-websocket-redis3

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* Keys for entries in Redis datastore can be prefixed by an optional string. This may be required
to avoid namespace clashes.

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* Added possibility to publish and subscribe for Django Groups, additionally to Users and Sesions.
* To ease the communication between Redis and the Django, a new class ``RedisPublisher`` has
been added as Programming Interface for the Django loop. Before, one had to connect to the Redis
datastore directly to send messages to the Websoclet loop.
* Renamed configuration setting ``WS4REDIS_STORE`` to ``WS4REDIS_SUBSCRIBER``.

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* Fixed: Use flush to discard received PONG message.

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* Moved mokey patching for Redis socket into the runner. This sometimes caused errors when
running in development mode.
* Added timeout to select call. This caused IOerrors when running under uWSGI and the websocket
was idle.

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* Reverted issue 1 and dropped compatibility with Django-1.4 since the response status must
use force_str.

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* Major API changes.
* Use ``WS4REDIS_...`` in Django settings.
* Persist messages, allowing server reboots and reconnecting the client.
* Share the file descriptor for Redis for all open connections.
* Allow to override the subscribe/publish engine.