RGBModel reset can be simplified

[samreid]

RGBModel implements reset like so:

      reset: function() {
        this.redIntensityProperty.value = 0;
        this.greenIntensityProperty.value = 0;
        this.blueIntensityProperty.value = 0;
        this.perceivedRedIntensityProperty.value = 0;
        this.perceivedGreenIntensityProperty.value = 0;
        this.perceivedBlueIntensityProperty.value = 0;

        this.redBeam.reset();
        this.greenBeam.reset();
        this.blueBeam.reset();
      }

But since the RGBModel inherits from PropertySet, I think the first 6 lines of that body can be replaced with:

PropertySet.prototype.reset.call( this );

[aaronsamuel137]

Assigning to @samreid for review

[samreid]

Looks good, thanks! Closing.