Sprint5 Version

Hi, I've updated the code once again with the following changes:

• I added the following files:

1. IObserver.h
2. ISubject.h
3. metaDataHelper.h
4. metaDataHelper.cpp

• I also adjusted the GUI to include:

1. Thumbnail
2. Artist Name
3. Album Name
4. Music duration slider
5. Pause/Play Button
6. Ability to load next track when reaching the end of the current track.