Drop six requirement, use django.utils.six instead (#282)

* Drop six requirement, use django.utils.six instead

* Drop six requirement, use django.utils.six instead

* Make isort happy

django_select2/forms.py

@@ -58,8 +58,7 @@ from django.core.urlresolvers import reverse
 from django.db.models import Q
 from django.forms.models import ModelChoiceIterator
 from django.utils.encoding import force_text
-
-from six.moves.cPickle import PicklingError as cPicklingError
+from django.utils.six.moves.cPickle import PicklingError as cPicklingError
 
 from .cache import cache
 from .conf import settings

tests/test_forms.py

@@ -9,8 +9,8 @@ from django.core import signing
 from django.core.urlresolvers import reverse
 from django.db.models import QuerySet
 from django.utils.encoding import force_text
+from django.utils.six import text_type
 from selenium.common.exceptions import NoSuchElementException
-from six import text_type
 
 from django_select2.cache import cache
 from django_select2.forms import (