Add ys (y scale)

torus.scad

@@ -1,6 +1,6 @@
-module torus(r_major, r_minor, xs=1.0) {
+module torus(r_major, r_minor, xs=1.0, ys=1.0) {
     rotate_extrude()
     translate([r_major, 0, 0])
-    scale([xs, 1.0, 1.0])
+    scale([xs, ys, 1.0])
     circle(r=r_minor);
 }