My configuration files for Emacs and more. It uses pallet.
Move the Cask file to ~/.emacs.d/ and then you should be able to do M-x pallet-mode and then M-x pallet-install and have it auto-install everything.
elm-mode, elm-oracle autocomplete (you have to install elm-oracle on your own), flycheck.
If autocomplete doesn't work try cleaning all the compilation artifact and elm-package.json and start compiling from scratch.
flycheck, autocomplete, distel
ido everywhere, etc