Add ability to drain redis queue before closing logger, update Redis client library version

[thecubed]

No description provided.

[yads]

What happens if the drain event is never emitted?

[thecubed]

I believe if the 'drain' event isn't emitted by the Redis library that the logger will hang until Redis's queue is empty. This would prevent messages from being dropped that were queued when the log.close() method is called.

I can check and see if there's a way to have Winston pass a value along to us that allows for force closing the connection by default or to wait for the drain event and close gracefully if set.

[yads]

@thecubed I think that would be preferable, thanks.