I completed converting game_stub to game for Nim.

My strategy was to use the game.py from Tic Tac Toe and try to compare
what was happening in Nim to TTT.

play_nim.py

@@ -1,11 +1,11 @@
-from nim.game_stub import NimGameStub
+from nim.game import NimGame
 from nim.view import NimView
 from nim.player import HumanNimPlayer, ComputerNimPlayer
 
 player0 = HumanNimPlayer(input("What's your name? "))
 player1 = ComputerNimPlayer("Robot")
 view = NimView(player0, player1)
-game = NimGameStub()
+game = NimGame()
 
 view.greet()
 state = game.get_initial_state()