Added room tracking for snake body

- Game now can track your last <snake length> rooms, in order, and
detect when  you're moving into a room already in this list
- Right now this doesn't happen automatically, to test it out call the
command "testit" after each time you do a room change
- Added debug info for room tracking, use command "debug" to turn this
on
- ctrl-f "TODO" to find work that should be added. Hopefully I can
tackle most of this tomorrow, but I have some other homework to look at
as well.