Composer's autoload mechanism fails to load PHP-ActiveRecord classes

PHP-ActiveRecord doesn't actually follow PSR-0 convention, e.g. `ActiveRecord\Config` should be in `lib/ActiveRecord/Config.php` and not `lib/Config.php`.  Fortunately, loading the `ActiveRecord.php` file loads the common dependencies and registers an autoloader The Old Fashioned Way, and Composer has a config option for that.