Gets or sets the global timeScale which is a multiplier that affects ALL animations equally. This doesn't actually set the timeScale()
of each individual tween/timeline, but rather it affects the rate at which the root timeline plays (that timeline contains all other animations). This is a great way to globally speed up or slow down all animations at once. For example:
TweenMax.globalTimeScale(0.5); //plays at half-speed
TweenMax.globalTimeScale(2); //plays twice the normal speed
var currentTimeScale = TweenMax.globalTimeScale(); //returns the current global timeScale