public static function autoload($class)
    {
        if (0 === strpos($class, 'Bitpay\\')) {
            $classname = substr($class, 7);

            $file = __DIR__.DIRECTORY_SEPARATOR.str_replace('\\', DIRECTORY_SEPARATOR, $classname).'.php';

            if (is_file($file) && is_readable($file)) {
                require_once $file;

                return true;
            }

            throw new \Exception(sprintf('Class "%s" Not Found', $class));
        }
    }