title: Django countries not show country list
body: <p>I have problem in Django countries. I install it (over pip), run makemigrations, run migrate, and added on my settings.py django-countries in INSTALLED_APPS </p>
  
  <p>In model file i have:</p>
  
  <pre><code>from django_countries.fields import CountryField
  class Server(models.Model):
      country = CountryField()
  </code></pre>
  
  <p>But when i create new server in django admin, i see empty select. 
  I read <a href="https://pypi.python.org/pypi/django-countries" rel="nofollow">this</a> and <a href="https://github.com/SmileyChris/django-countries" rel="nofollow">this</a>, but this manuals do not give us anything new. </p>
  
  <p>Please, tell me, what should I do to make it work?</p>