title: Error with urlFor() on Slim + Twig
body: <p>I get a error where Slim says </p>
  
  <pre><code>Message: An exception has been thrown during the rendering of a template 
  ("Named route not found for name: userList") in "sidebar.twig" at line 7.
  </code></pre>
  
  <p>My view is 
  </p>
  
  <pre><code>{% extends 'base.twig' %}
  {% block title %} Índice {% endblock title %}
  
  {% block content %}
  &lt;div class="row"&gt;
      &lt;div class="container"&gt;
      {% include "sidebar.twig" %}
  </code></pre>
  
  <p>My view sidebar.twig is as below:
  </p>
  
  <pre><code>&lt;div class="col-lg-4 col-md-4 col-xs-4"&gt;
      &lt;div class="dropdown menu col-lg-9 col-md-9 col-xs-9"&gt;
          &lt;ul class="nav nav-pills nav-stacked"&gt;
              &lt;li&gt;&lt;a tabindex="-1" href="#"&gt;GESTIÓN DE PARTICIPANTES&lt;/a&gt;&lt;/li&gt;
              {% if authorized %}
              &lt;li&gt;&lt;a tabindex="-1" href="{{ urlFor('userList') }}"&gt;GESTION DE USUARIOS&lt;/a&gt;&lt;/li&gt;
              {% endif %}
          &lt;/ul&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>code for view + model
  </p>
  
  <pre><code>$app-&gt;get('/users', function() use ($app, $authorized,$users)
  { 
      $app-&gt;render('users.twig',array('users' =&gt; $users, 'is_admin' =&gt; $authorized));
  })-&gt;name('userList');
  </code></pre>
  
  <p>Code in github is => <code>https://github.com/Mangulomx/olimpiada</code></p>