begin OO refactor

- create new connect4 game
- can initalize game
- create board object
- can intialize and display board
- create players object
- can intialize game's players
edit new take_turn method

- first turn can be taken
- move can be checked for validity
- must add make_move method to board object
- must add game_over? check
can check for win

- can check horizontal and vertical win condition
- refactor to know last column value instead of num_columns
- can edit board when move made
- can check if game over
- can check stalemate
finish game (untested)

- add winner, stalemate, and new game conditions
- some general method name refactoring
- all game parts in place but untested