Make redis configurable.

Adds options to configure the redis connections:

* redisHost: The host where redis client should connect to
* redisPort: The port of the redis server

These two options above are used for client connections: subscriptions
to pubsub channels.

You can also customize the location of the publishing redis server
(which may be different if you use master/slave replication).

* publishHost: The host where the redis publisher should connect to
* publishPort: The port of the redis master server