added demo game in chris_demo

You had some really clear planning in your commit message--
In the "chris_demo" folder I implemented a bunch of what
you planned. I suggest playing the game I built
(go into chris_demo and run python game.py), and then
carefully reading all the source code. Then, if you like
the patterns I used, copy or move whatever you want
to use into your main project folder. Also, if there
are parts of my code you don't understand, please let
me know (in a commit message or in person next time
I'm in class) and I'll be happy to explain it.

chris_demo/game.py

@@ -0,0 +1,11 @@
+from retro.game import Game
+from dealer import Dealer
+
+dealer = Dealer((1, 1))
+state = {
+    "score": 0, 
+    "options": "h to hit or s to stay",
+}
+game = Game([dealer], state)
+game.play()
+