public function postCsv()
 {
     $mailing = Mailing::all();
     $file_path = 'mailing.csv';
     $dados = '';
     $dados .= 'EMAIL';
     $dados .= "\n";
     foreach ($mailing as $m) {
         $dados .= $m->email;
         $dados .= "\n";
     }
     if (fwrite($file = fopen($file_path, 'w+'), $dados)) {
         fclose($file);
         return Response::download($file_path);
     }
 }