The ActiveRecord namespace doesn't follow PSR-0 conventions, so Composer's "psr-0" autoloader fails to autoload classes.

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.
Merge pull request #239 from ethos-development/master

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