Upgrading the base image to bitwalker/alpine-elixir:1.4.5 (with erlang 20.0.1 underneath) shaved off another 12 Mb down to 48 Mb. After looking at the size stats, the shrink is due to erts loosing some weight:
docker run -it gmile/ritm:0.0.10 du /app -h -d 1
21.1M /app/erts-9.0.1
52.0K /app/bin
380.0K /app/releases
22.2M /app/lib
43.7M /app
The size of erts is still way more than 6 Mb.
