Added licensing to Z-axis wobble fix

Z-Axis Wobble Fix/z-wobble.scad

+/*
+ * Created by:
+ * Thomas Buck <xythobuz@xythobuz.de> in May 2016
+ *
+ * Licensed under the Creative Commons - Attribution license.
+ */
+
+// -----------------------------------------------------------
 
 diameter_outer_min = 10;
 diameter_outer_max = 12;
 
 $fn = 20;
 
+// -----------------------------------------------------------
+
 difference() {
     cylinder(d1 = diameter_outer_max, d2 = diameter_outer_min, h = height);
     cylinder(d = diameter_inner_max, d2 = diameter_inner_min, h = height);