/**
  * Don't allow updates to credential - must use the ForgotCredentialToken instead
  *
  * @param type $id
  * @param type $data
  * @return type
  * @throws InvalidArgumentException
  */
 public function update($id, $data)
 {
     if (isset($data['credential'])) {
         throw new Exception\InvalidArgumentException('Credential cannot be updated. Use ForgotCredentialToken instead.');
     }
     return parent::update($id, $data);
 }