TST: Add output of answer key annotations to notebook.

For more improved viewing experience via nbviewer.ipyhton.org,
include the output of the notebook.

When saving/updating this file, a fresh kernel and evaluation of
the entire notebook should be used so that the cell numbers stay
in order.

tests/risk/AnswerKeyAnnotations.ipynb

@@ -30,7 +30,8 @@
       "import answer_key"
      ],
      "language": "python",
-     "outputs": []
+     "outputs": [],
+     "prompt_number": 1
     },
     {
      "cell_type": "code",
@@ -41,7 +42,19 @@
       "\"\"\".format(latest_answer_key_url=answer_key.LATEST_ANSWER_KEY_URL))"
      ],
      "language": "python",
-     "outputs": []
+     "outputs": [
+      {
+       "html": [
+        "<p>Download link for latest answer key: <a href=\"https://s3.amazonaws.com/zipline-test-data/risk/cc507b6fca18aabadac69657181edd4e/risk-answer-key.xlsx\">https://s3.amazonaws.com/zipline-test-data/risk/cc507b6fca18aabadac69657181edd4e/risk-answer-key.xlsx</a></p>"
+       ],
+       "output_type": "pyout",
+       "prompt_number": 2,
+       "text": [
+        "'\\nDownload link for latest answer key: [https://s3.amazonaws.com/zipline-test-data/risk/cc507b6fca18aabadac69657181edd4e/risk-answer-key.xlsx](https://s3.amazonaws.com/zipline-test-data/risk/cc507b6fca18aabadac69657181edd4e/risk-answer-key.xlsx)\\n'"
+       ]
+      }
+     ],
+     "prompt_number": 2
     }
    ]
   }