Allow additional query args to get_entries() via class extension,
by changing send_request() and prepare_response() from private to protected

EG:
class MM_GFWebAPIWrapper extends GFWebAPIWrapper {
  public function get_entries( $form_id, $search=null, $sorting=null, $paging=null, $query_more=null ){
    $form_id = absint( $form_id );

    $query['sorting'] = $sorting;
    $query['paging']  = $paging;

    if( ! empty( $query_more ) && is_array( $query_more ) ) {
      foreach( $query_more as $key => $val ) {
        $query[$key] = $val;
      }
    }

    $response = $this->send_request( 'GET', "forms/{$form_id}/entries", $query );

    return $this->prepare_response($response);
  }
}