Add 'Deploy to Heroku' button

[lukasz-madon]

an example https://github.com/lukasz-madon/hackers-job-apply

1. add app.json
2. copy Profile
3. add button [![Deploy to Heroku](https://www.herokucdn.com/deploy/button.png)](https://heroku.com/deploy)

[lukasz-madon]

for Windows users https://azure.microsoft.com/en-gb/blog/deploy-to-azure-button-for-azure-websites-2/