Describe physical network game

This is the game we played during the first run of this class, now written up
for others to replicate and improve.
Move demo instructions to README for easy viewing

Just to make GitHub show it while browsing the repo.
Tix fypo

I don't know what dmeoing is, but I don't think we should do it to children.
Merge pull request #1 from kristjan/physical_demo

Physical demo writeup