added cell changes that sends the get all values array to play in cell
added print board which show the board as an array of the values
added the exterminate which gets rid of possibilities
added need_guess method
made it so if impossible will still be able to print the board... I think
added the play method will solve easy problems
added get cell value to make it so board is less depended on cell.value
added inconceivable to the play method
Merge pull request #9 from kma3a/board4

Board4