Rails 2.3/Bundler: auto-add lib to autoload_paths

This change makes Rails 2.3 automatically add the lib folder to the autoload_paths when installing acts_as_taggable_on_steroids as a Gem and load it via Bundler/Gemfile. Without this change, Rails 2.3 will only autoload when requiring via config.gem.

Does this have any unintended side-effects when installing as a plugin on Rails 2.3 or as a plugin/gem on Rails 3?