Merge pull request #131 from ryanpeach/patch-2

NoOutputFilter isn't set in tutorial.

tutorials/2. Adding an Environment.ipynb

@@ -189,7 +189,7 @@
     "    def __init__(self):\n",
     "        super().__init__()\n",
     "        self.default_input_filter = NoInputFilter()\n",
-    "        self.default_output_filter = NoInputFilter()\n",
+    "        self.default_output_filter = NoOutputFilter()\n",
     "\n",
     "    @property\n",
     "    def path(self):\n",