Completed the retro lab, making changes so it'd work.

In asteroid.py line 14, I changed HEIGHT to game.board_size[1]
In asteroid.py line 15 I changed game.remove_agent_by_name(self.name) to game.remove_agent(self)

Was the code given on the page supposed to work as
is? It read like it should have just been a copy+
paste+run, but I had to make the above changes to
do so. For example, I don't think asteroid objects
have names, so you can't remove them by name? And
nowhere was HEIGHT defined.

try.py

@@ -0,0 +1,10 @@
+# Was supposed to try this per the introduction to retro, but this doesn't
+# actually seem to work? I keep getting an error...
+
+from retro.game import Game
+from retro.agent import ArrowKeyAgent
+
+agent = ArrowKeyAgent()
+state = {}
+game = Game([agent], state)
+game.play()