Depth first for pegs problem
added todo
Added Gobbler game
138,724 nodes in 5 seconds.
212,027 nodes in 5 seconds.
212,027 nodes in 5 seconds.

Got rid of square, but it didn't change
things at all. Does scala treat unary
case classes like haskell newtypes?
286,731 nodes in 5 seconds

Well, it is better. I was hoping for a lot more.
better toString
286,731 in 5 seconds.

arrays have same performance as vectors?
402,417 in 5 seconds.

Reduced width of search tree.