fix dennybritz#89

Author: Aerin Kim

DQN/Breakout Playground.ipynb

@@ -73,7 +73,7 @@
    ],
    "source": [
     "print(\"Action space size: {}\".format(env.action_space.n))\n",
-    "print(env.get_action_meanings())\n",
+    "print(env.get_action_meanings()) # env.unwrapped.get_action_meanings() for gym 0.8.0 or later\n",
     "\n",
     "observation = env.reset()\n",
     "print(\"Observation space shape: {}\".format(observation.shape))\n",