[MLB] Add new extractor

Please review and merge the new extractor for MLB.com
I've tried http://mediadownloads.mlb.com/mlbam/2014/07/12/ in a browser and it takes more than 50 seconds to download. We should use a faster method, for example looking into: http://m.mlb.com/gen/multimedia/detail/6/6/3/34496663.xml