title: Can't get heroku procfile
body: <p>I'm trying to build up a deep-learning-based facebook chatbot (using Python). I'm trying to deploy it on <a href="https://www.heroku.com/" rel="nofollow noreferrer">Heroku</a> firstly, but as I'm using the command <code>web: gunicorn echoserver:app</code> the terminal says <code>web: command not found</code>. Howevere, I've installed <code>gunicorn</code> already.</p>