Erin the Erlang Installer

This applescript returns a list of Erlang versions installed by Homebrew and presents a choice to switch versions. It then opens an erl shell with the chosen version.

Instructions:

1. Clone or download the repository and unzip it
2. Run Erin.app by double-clicking

Planned future improvements:

1. To check if Homebrew is installed
2. To present an option to install / upgrade current version
3. To highlight current version
4. catch exceptions when Cancel is clicked