add multiply_row and multiply_column to TTT class, allows you to calculate products of a given row and given column and tests
add multiply_diagonal which returns product of all elements in a given diagonal of the board, add possible_win? which returns boolean as to whether or not a given player can win in the next turn
add pseudocoding logic for making a move(first step)
add player class refactor code so possible_win? belongs to player, and refactor tests accordingly
refactor code so assign_spot is in player class, add tests accordingly
separate player, and controller classes into different files