Improve spacing and indentation.

app/templates/signup.html

@@ -118,20 +118,18 @@ h1{
 </style>
 
 <div class="container">
+
   <section class="signin-heading">
     <h1>Sign Up</h1>
   </section>
 
   <form action="/signup" method="POST">
     <p><input type="username" name="username" placeholder="输入用户名" required="required" class="username"></p>
-
     <p><input type="password" name="password" placeholder="输入密码" class="password"></p>
-
     <p><input type="password" name="password2" placeholder="确认密码" class="password"></p>
-
     <button type="submit" class="btn">注册</button>
-
   </form>
+
 </div>
   
 {% endif %}