Use multiple buildpacks on your app
$ heroku buildpacks:set https://github.com/moveline/heroku-buildpack-multi.git
$ cat .buildpacks
https://github.com/heroku/heroku-buildpack-nodejs.git#0198c71daa8
https://github.com/heroku/heroku-buildpack-ruby.git#v86
MIT