完成评论功能

1. 定义评论的视图函数
   @app.route('/comment/',methods=['POST'])
   def comment()：
   读取前端页面数据，保存到数据库中
2. 用<input type="hidden" 方法获取前端的"question_id" 
3. 显示评论次数
4. 要求评论前登录
5. 尝试实现详情页面下的评论列表显示

   @app.route('/detail/<question_id>')
   def detail(question_id):
       quest= Question.query.filter(Question.id == question_id).first()
       return render_template('detail.html',ques=quest)
   @app.route('/comment/', methods=['POST'])
   def comment():
       comment_detail = request.form.get('new_comment')
       ques_id = request.form.get('question_id')
       auth_id = User.query.filter(User.username == session.get('user')).first().id
       comm = Comment(detail=comment, author_id=auth_id, question_id=ques_id, )
       db.session.add(comment)
       db.session.commit()
       return redirect(url_for('detail', question_id=ques_id))
   def loginFrist(func):
       @wraps(func)
       def wrapper(*args, **kwargs):
           if session.get('user'):
               return func(*args, **kwargs)
           else:
               return redirect(url_for('login'))
       return wrapper

   <div class="essayAera">
       <h3>{{ ques.title }}<br><small>{{ ques.author.username }}<span class="badge">{{ ques.create_time }}</span></small></h3>
   </div>
   <p class="lead">{{ ques.detail }}</p>
   <hr>
   <form action="{{ url_for('comment') }}"method="post">
   <ul class="list-group">
   
                          <div class="form-group">
                          <textarea name="new_comment"class="form-control"style="margin-top:80px " rows="6" cols="50" id="new_comment"placeholder="write down your comment"></textarea>
                              <input name="question_id"type="hidden"value="{{ ques.id }}"/>
   
                          </div>
                              <button type="submit" class="btn btn-default">发送</button>
   
   
                          </ul></form>
   
   <h4>评论.({{ ques.comments|length }})</h4>
   
   {% endblock %}