Add rbenv and git cookbooks (rbenv depends on git)
Add rbenv/ruby_build to run list and install Ruby, Bundler & Rails
Make .gitignore more explicit for data_bags & www directories
Add ohai, postgresql & tmux cookbooks
Split webserver role into multiple roles (base/ruby/php)
Update README with new repo name & description
Configure VM for Ruby development

rbenv and ruby-build are included so that it's possible to maintain
multiple Ruby versions and Gem sets.