function moveTowardsLength(movingPoint, targetPoint, amount) {
          var width = targetPoint.x - movingPoint.x;
          var height = targetPoint.y - movingPoint.y;
          var distance = Math.sqrt(width * width + height * height);
          return moveTowardsFractional(movingPoint, targetPoint, Math.min(1, amount / distance));
        }
SVG Path rounding function. Takes an input path string and outputs a path
string where all line-line corners have been rounded. Only supports absolute
commands at the moment.

@param pathString The SVG input path
@param radius The amount to round the corners, either a value in the SVG
              coordinate space, or, if useFractionalRadius is true, a value
              from 0 to 1.
@returns A new SVG path string with the rounding