Add description method to SVGLength.
Add description method to SVGLength.

MaddTheSane/SVGKit,MaddTheSane/SVGKit,seltzered/SVGKit,MaddTheSane/SVGKit,seltzered/SVGKit,MaddTheSane/SVGKit,seltzered/SVGKit,seltzered/SVGKit,MaddTheSane/SVGKit,seltzered/SVGKit,seltzered/SVGKit