Merge pull request #185 from kswiat/adjust_to_new_django_versions

Adjust render_django_response() to Django>1.4

pygal/ghost.py

@@ -146,7 +146,7 @@ class Ghost(object):
     def render_django_response(self, **kwargs):
         """Render the graph, and return a Django response"""
         from django.http import HttpResponse
-        return HttpResponse(self.render(**kwargs), mimetype='image/svg+xml')
+        return HttpResponse(self.render(**kwargs), content_type='image/svg+xml')
 
     def render_to_file(self, filename, **kwargs):
         """Render the graph, and write it to filename"""