Setting manual logging level

You can specify the logging level when creating the RedisNotifier object; not sure if this is how you wanted that to work but we can probably talk this out :)

Example usage:

```javascript
var sub = new notifier(redis, {
    redis : { host : config.redis.host, port : config.redis.port },
    expired : true,
    evicted : true,
    logger : {
      level: 'ERROR'
    }
  });
```