Implemented all pre-existing tests.
Created Tennis::Game#wins_ball. Expanded Tennis::Game#score to return correct string score for @points 0 through 3.
Add failing test for when a player wins 4 points to 2
Expand Tennis::Player#score to return 'win' when this player has won.
Add failing test for when player wins 6 to 4.
Refactored code on line 44 to account for when game goes past first 4 points.
Add failing test for when score is deuce.
Expand Tennis::Player#score to return 'deuce' when players have more than 3 points and are tied.
Add failing test for when player has 1 more point than opponent.
Expand Tennis::Player#score to return 'ad player' when player has more than 3 points and 1 more point than opponent.
Add failing test for when opponent has more than 3 points and has 1 more point than player
Expand Tennis::Player#score to return 'ad opponent' if players have more than 3 points and opponent is winning by 1.