Install Elixir and Phoenix on macOS

install_elixir_phoenix.sh

# Update brew
brew update

# Need postgres
brew install postgresql

# Install elixir
brew install elixir

# Install hex package manager
mix local.hex

# Start postgres
brew services start postgresql

# Optional install default postgres user
createuser -d postgres

# Install phoenix
mix archive.install hex phx_new

1. brew install asdf
2. thoughtbot/dotfiles#577 (comment)

$ asdf plugin add erlang
$ asdf install erlang
$ asdf global erlang 
$ asdf plugin add elixir
$ asdf install elixir
$ asdf global elixir