Change effective on 11 December 2013
Procfile is no longer required to run a Node.js app on Heroku. If no
Procfile is present in the root directory of your app during the build process, we will check for a
scripts.start entry in your
package.json file. If such an entry is present, a default Procfile is generated automatically:
$ cat Procfile web: npm start
For more info, see the documentation.