I think You can do it by yourself…
I remember generating some phoenix docs with
$ git clone https://github.com/phoenixframework/phoenix.git
$ cd phoenix
$ mix deps.get
$ mix docs --formatter epub
It is just a bit more complex with Elixir, because You need to update Makefile
$ git clone https://github.com/elixir-lang/elixir-lang.github.com.git
$ git clone git://github.com/elixir-lang/ex_doc.git
$ cd ex_doc && ../elixir/bin/mix do deps.get, compile
$ cd ../elixir
$ vim Makefile
#==> Documentation tasks
# DOCS_FORMAT = html
DOCS_FORMAT = epub
$ make docs
That might be outdated, as I did this last year with Elixir 1.5.x
