public function postSurvey(Request $request)
 {
     $this->validate($request, ['email' => 'required|email']);
     $survey = Survey::firstOrNew(['email' => $request->input('email')]);
     if (!$survey->exists) {
         $survey->current_step = 1;
         $survey->save();
     }
     $request->session()->put('survey_id', $survey->id);
     return redirect()->action('SurveyController@getSurveyStep', ['step' => $survey->current_step]);
 }