Remove Transition ! Close #2

Transition aren't so usefull and are very hard to implement if you want
it safe.

The Time Transition value may be altered by diffenrent Music Duration
and more with short Music

The volume cant be restitued if stop() is effectued while the Music is
playing...

And update(dt) need to be process each instant if you want a perfect
calcul of volume, and that's why a perfect volume is impossible and if
you store the volume in file (like i've done), you may see that the
volume saved isn't exactly the same each time you run your app.