ScoreTracker that we'll use to keep track of the scores of two players who are
playing a game.
Players playing this game always take turns, and Player 1 always plays first.
Both players scores start at zero.
ScoreTracker should provide a method
score that accepts a number of points and does not return a value.
If it is Player 1's turn, the points (which might be negative) get added to their score.
Otherwise they get added to Player 2's score.
You should also provide a method
currentlyAhead that returns
1 if Player 1 is ahead,
2 if Player 2 is ahead,
0 if it's a tie.
You should not expose any of your state publicly, and
ScoreTracker does not need to provide a public constructor.
When your class is complete, here is how it should work: