Subscription termination - add charge argument

[kai11]

https://dev.recurly.com/docs/terminate-subscription mention charge argument, but it's not in library.
Please fix.

Until this is fixed, my monkey patch can be useful for others:

class Recurly_SubscriptionEx extends \Recurly_Subscription {
    public static function get($uuid, $client = null) {
        Recurly_Resource::$class_map['subscription'] = 'Recurly_SubscriptionEx';
        $ret = \Recurly_Base::_get(\Recurly_SubscriptionEx::uriForSubscription($uuid), $client);
        Recurly_Resource::$class_map['subscription'] = 'Recurly_Subscription';
        return $ret;
    }
    public function terminateEx($refundType, $charge) {
        $this->_save(\Recurly_Client::PUT, $this->uri() . '/terminate?refund=' . $refundType . '    &charge=' . ($charge ? 'true' : 'false'));
    }
}