fix django 3 compitability

.gitignore

@@ -10,3 +10,4 @@ db.sqlite
 *.egg-info
 *.pyc
 *.swp
+venv/

README.rst

@@ -21,7 +21,7 @@ This is where autofixtures will help!
 Requirements
 ============
 
-* We require and support Django 1.4 to 1.9
+* We require and support Django >= 1.4
 
 
 Installation

autofixture/base.py

@@ -3,7 +3,7 @@
 from django.db.models import fields, ImageField
 from django.conf import settings
 from django.db.models.fields import related
-from django.utils.six import with_metaclass
+from six import with_metaclass
 
 import autofixture
 from autofixture import constraints, generators, signals

autofixture/values.py

@@ -1,4 +1,4 @@
-from django.utils.six import with_metaclass
+from six import with_metaclass
 
 
 class ValuesMetaclass(type):