See #4 for details.

Adds compatibility for Omnipay v3.x.

Adds support for using a Direct Post API payment_token created via Collect.js in place of credit card number and expiration date.

Example usage:

$gateway = Omnipay::create('NMI_DirectPost');
$response = $gateway
  ->createCard(['card' => $data['billing_data'])
  ->setPaymentToken($data['payment_token'])
  ->send();