GameManager specifications
npublic GameManager (Player player1,   Player player2) n Create a nim GameManager, with the specified players; by default, the first Player specified plays first in the first game.
n require:
n player1 != null
n player2 != null
n
npublic int sticksLeft ()
n The number of sticks in the Pile.
n ensure:this.sticksLeft() >= 0
n
n