Elixir + Iconv Dockerfile

$ VERSION=latest FOLDER=1.3 make build
$ VERSION=latest make push

# Build and push together
$ VERSION=latest FOLDER=1.4 make all

This Dockerfile enables you to use Iconv within your Elixir project.
Also added Imagemagick.

This Dockerfile is based on the elixir.

Have fun and feel free to submit any changes!