added creation of new board with pieces and checkers class
fixed grid assiment helper methods ([] and []=)
added Board#move_valid?
added Board#render
in process of creating Board#valid_step_move?
added Board#valid_step_move? Board#make_move! and Checker#piece_moves
added Board#valid_jump_moves
changes valid_jump_moves to valid_jump_move?
added HumanPlayer class and Gameclass including game loop. need to debug
cleaned out bugs from last commit.
added piece promotion
moved folders
adding previous week2 work