Use git shallow clone to improve cloning performance

AIDungeon_2.ipynb

@@ -45,7 +45,7 @@
         "colab": {}
       },
       "source": [
-        "!git clone https://github.com/nickwalton/AIDungeon/\n",
+        "!git clone --depth 1 https://github.com/nickwalton/AIDungeon/\n",
         "%cd AIDungeon\n",
         "!./install.sh\n",
         "from IPython.display import clear_output \n",
@@ -71,4 +71,4 @@
       "outputs": []
     }
   ]
-}
+}