Add #possible_jump_moves
Make Piece#jump_moves recursively find multiple-jump moves
Refactor #jump_moves
Reorganize Piece
progress on jump moves, not there yet
prepare to rewrite jump_moves
Piece#jump_moves finally working recursively
Remove old #jump_moves
Move #trace_path to private, remove debugging info
Refactor #valid_jumps and #slide_moves
Add basic board evaluation
Add #negamax method
Changes to Board and Piece for Negamax compatibility
Add MoveNode#children
varname fix
Ready to begin debugging
Change board from ivar to arg
Fix color to ivar
Functioning but not working
Fix #pieces to work when passed a color