v1.13

18 July 2013 : Added hub_type "no" used for push-fit axles
v 1.12, 18 July 2013 : Added spoke_type "spring", spring_segments
variable, changed "double_left" to "spiral_left_double", "double_right"
to "spiral_right_double", "left" to "spiral_left" and "right" to
"spiral_right"
v 1.11, 19 June 2013 : Added small spacing between double spokes
v 1.10, 18 June 2013 : Fixed hub high for the screw to be able to be
bolted