Allowing AUTH usage for redis

I've adding a check to see if password is set in the database config. If so, send the AUTH command: http://redis.io/commands/auth.

Before trying to select the DB, I send a ping command to ensure that the server doesn't require authentication or that authentication was successful. 

By splitting this into two calls, we can have a password set in the config even though the server doesn't require it and operation will continue without exception. This allows for graceful migration of the server to using AUTH.