Support for redis sentinel in redis input and output

Redis supports failover through a separate service called Sentinel (http://redis.io/topics/sentinel). I added support for it to the output and input modules using the redis-sentinel wrapper library (https://github.com/flyerhzm/redis-sentinel).
Maybe this should be a required setting, unless it's really common that users would have their sentinel master set named 'mymaster' ? I see the redis docs use this as an example. On the other hand, it might be confusing if master were required only if sentinels were in use. Hmm..

Thoughts?