setup-ruby-environment

### Changelog
* added in reference to devenvironment cookbook
* https://trello.com/c/fMn4uO5G/339-update-kitchenplan-to-install-ruby-2-1-3-as-default-system-ruby
* link to cookbook repo: https://github.com/cgullick/chef-devenvironment
move this out of default recipe and into the developer.yml file instead.  EIR's don't need to install ruby/rbenv.