Christmas lights

This is an exercise that we made up to try and bridge the gap between other exercises and Christmas Tree.

This is accompanied by this video: https://www.youtube.com/watch?v=PhCEgCPrmBE

Description

Your goal is to represent a wire with christmas lights on it. You should be able to call add_to_chain to add a light to the end of the wire.

You should also be able to print out the list of wires.