Initial Piece method
Initial Board methods
Have working piece#move functions, refactor Board to use #[]
Add board coloring
HumanPlayer placeholder
Add Board#dup and Piece#dup
Add Piece#valid_move_seq?
Move Piece#perform_move! to private
Add Piece#perform_moves
Bugfixes
Start Checkers class, move player initialization to Checkers
Add Checkers#play
Bugfixes and refinements
Add piece promotion and jump checking
fix jump checking
Use unicode symbols
Add indices on Board#render
Make Piece#jump_moves and Piece#slide_moves public
Begin ComputerPlayer
Revert "Make Piece#jump_moves and Piece#slide_moves public" (wrong branch)

This reverts commit 2f68295d1668c4f8075f5e1bd148dcfc518283a3.