Add current time / duration

[leandromoreira]

It's important if the user wants to keep track of in what happened in a given time, mostly for VOD. Therefore we might deduce X %.

extra: {
   duration: 50004, // in ms
   currentTime: 4504, // in ms
   watchedPercentage: (watch / duration) * 100,// in ms
   bufferingPercentage: (buffering  / watch) * 100,// in ms
}