title: Error using xadmin
body: <p>This is my registered xadmin APP</p>
  
  <pre><code> INSTALLED_APPS = [
      'django.contrib.admin',
      'django.contrib.auth',
      'django.contrib.contenttypes',
      'django.contrib.sessions',
      'django.contrib.messages',
      'django.contrib.staticfiles',
      'users',
      'courses',
      'operation',
      'organization',
      'xadmin',
      'crispy_forms'
  ]
  </code></pre>
  
  <p>This is the urls</p>
  
  <pre><code>from django.conf.urls import url
  from django.contrib import admin
  import xadmin
  
  urlpatterns = [
      # url(r'^admin/', admin.site.urls),
      url(r'^xadmin/', xadmin.site.urls),
  ]
  </code></pre>
  
  <p>But I don't know what to do with this problem, I just started to learn django</p>
  
  <pre><code>  File "C:\Users\PC_LF\Envs\testvir2\lib\site-packages\xadmin\__init__.py", line 4, in &lt;module&gt;
      from xadmin.sites import AdminSite, site
    File "C:\Users\PC_LF\Envs\testvir2\lib\site-packages\xadmin\sites.py", line 3, in &lt;module&gt;
      from future.utils import iteritems
  ImportError: No module named 'future'
  </code></pre>