Updated to be usable with customizer

We build things with pipes around here. Stair rails, hammock stands, whatever. That tends to leave ugly, harsh ends on the pipe. They collect dirt, attract pests. and are a pain to grab a hold of.

This openscad file lets you set the inside & outside diameter of the pipe (because those are more likely to be known and easier to measure than the radii), and provides appropriate inner an outer flanges for the pipe.