Added django 1.9 check to transform expansion

Author: Ryan P Kilby

rest_framework_filters/utils.py

@@ -1,6 +1,7 @@
 
 from collections import OrderedDict
 
+import django
 from django.db.models.constants import LOOKUP_SEP
 from django.db.models.expressions import Expression
 from django.db.models.lookups import Transform
@@ -14,7 +15,7 @@ def lookups_for_field(model_field):
     lookups = []
 
     for expr, lookup in six.iteritems(class_lookups(model_field)):
-        if issubclass(lookup, Transform):
+        if issubclass(lookup, Transform) and django.VERSION >= (1, 9):
             transform = lookup(Expression(model_field))
             lookups += [
                 LOOKUP_SEP.join([expr, sub_expr]) for sub_expr