Fixed the issue with the touch area on the custom slider knob in Molecules and Light.  This involved changing HSlider node to only override the touch area if a custom knob is not specified.  See https://github.com/phetsims/molecules-and-light/issues/100.
Fixed the issue with the touch area on the custom slider knob in Molecules and Light.  This involved changing HSlider node to only override the touch area if a custom knob is not specified.  See https://github.com/phetsims/molecules-and-light/issues/100.

phetsims/sun,phetsims/sun,phetsims/sun