public function store(Request $request)
 {
     $this->validate($request, ['nickname' => 'required|unique:leaves|max:255', 'content' => 'required']);
     $leave = new Leave();
     $leave->nickname = Input::get('name');
     $leave->content = Input::get('comment');
     if ($leave->save()) {
         return Redirect::to('home');
     } else {
         return Redirect::back()->withInput()->withErrors('保存失败!');
     }
 }