See http://www.phoenixframework.org/docs/heroku
$ heroku create --buildpack "https://github.com/HashNuke/heroku-buildpack-elixir.git"
$ heroku buildpacks:add https://github.com/gjaldon/heroku-buildpack-phoenix-static.git
$ heroku git:remote -a [app-name]
config/prod.exs
config/prod.secret.exs
Procfile
MIX_ENV=prod mix phoenix.server
$ heroku run "POOL_SIZE=2 mix ecto.migrate"