Started working on an interactive tutorial.

I just added a draft of an interactive tutorial which you can look at in the 4dchessv4.0 Snapshot. So far it just sort of goes over how spaces are related on a 4D board starting out with a 1D board and working up to 4D. It might not display correctly if the window isn't tall enough (and the ideal height could potentially be higher that the height of your monitor) but I'll fix that another day.