Move some structure to child files, allows more flexibility

templates/login.html

@@ -1,5 +1,6 @@
 {% extends "layout.html" %}
 {% block body %}
+<div class="container">
 <form  method="post" role="form" data-toggle="validator">
   <div class="form-group has-feedback">
     <label class="control-label col-sm-4" for="username">Username:</label>
@@ -21,6 +22,7 @@
     </div>
   </div>
 </form>
+</div>
 
 
 {% endblock %}