No longer using requirements.txt but Pipfile.

Updates template to reflect that requirements.txt has been superseded by Pipfile.

hello/templates/index.html

@@ -25,7 +25,7 @@ <h3><span class="glyphicon glyphicon-info-sign"></span> How this sample app work
       <ul>
         <li>This app was deployed to Heroku, either using Git or by using <a href="https://github.com/heroku/python-getting-started">Heroku Button</a> on the repository.</li>
 
-        <li>When Heroku received the source code, it fetched all the dependencies in the <a href="https://github.com/heroku/python-getting-started/blob/master/requirements.txt">requirements.txt file</a>, creating a deployable slug.</li>
+        <li>When Heroku received the source code, it fetched all the dependencies in the <a href="https://github.com/heroku/python-getting-started/blob/master/Pipfile">Pipfile</a>, creating a deployable slug.</li>
         <li>The platform then spins up a dyno, a lightweight container that provides an isolated environment in which the slug can be mounted and executed.</li>
         <li>You can scale your app, manage it, and deploy over <a href="https://addons.heroku.com/">150 add-on services</a>, from the Dashboard or CLI.</li>
       </ul>