Save logs on separate Redis list based on their levels

[diogogmt]

Instead of saving all logs in a single list they could be saved on separate lists and use the log's level to generate the key name.

[indexzero]

@diogogmt This is wrong, but I understand what feature you need. On every call to .log() we attempt to coerce a string from the this.container function. Only the metadata is passed to this function, you want the level and msg passed as well.

I'm totally OK with this, just submit a different PR. Then you could do something like:

  var redisTransport = new require('winston-redis').Redis({
    container: function (level, msg, meta) {
      return 'OHAI:' + level;
    }
  });

[indexzero]

The two lines in question are here FYI. https://github.com/indexzero/winston-redis/blob/master/lib/winston-redis.js#L81-L82

This will be a breaking change, but I like the direction it's going in so I'm fine with that.