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

   @app.route('/comment/',methods=['POST'])
   @loginFirst
   def comment():
       comment=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(author_id=auth_id,question_id=ques_id,detail=comment)
       db.session.add(comm)
       db.session.commit()
       return redirect(url_for('detail',question_id=ques_id))

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

   {% extends'base.html' %}
   {% block title %}
       问答详情
   {% endblock %}
   {% block head %}
       <link rel="stylesheet" href="{{ url_for('static',filename='css/detail.css')}}" type="text/css">
   {% endblock %}
   {% block main %}
   
   <div class="content">
       <h3>标题：{{ ques.title }}<br><br><small>作者：{{ ques.author.username }} <br>
           <span class="badge">发布时间：{{ ques.create_time }}</span> </small></h3>
   <hr>
   <p class="lead">内容：{{ ques.detail }}</p>
   <hr>
   
       <form action="{{ url_for('comment') }}" method="post">
          <textarea class="comment" rows="8"  placeholder="写下你的评论："  name="new_comment"></textarea>
       <input name="question_id" type="hidden" value="{{ ques.id }}" />
       <button class="button" >发布 </button>
       </form>
   
   <span class="tcomment">评论：({{ ques.comments|length }})</span>
   <ul class="list-group">
    {% for foo in ques.comments %}
         <li class="list-group-item">
           <span class="glyphicon-leaf" aria-hidden="true"></span>
                 <img id="qu" src="{{ url_for('static',filename='images/question.jpg')}}"><a href = "">{{ foo.author.username }}</a>
          <span class="badge">评论时间：{{ foo.create_time }}</span>
           <p style="text-align: left">{{ foo.detail }}</p>
   
   
   </li>
   
       {% endfor %}
     </ul>
   </div>
   
   
   {% endblock %}