Support for django 3.0 and 3.1

Author: pterk

setup.py

@@ -7,9 +7,9 @@
     README = readme.read()
 
 if sys.version_info < (3, 0, 0):
-    django = 'django>=1.8.10,<2.0'
+    django = 'django>=1.11.29,<2.0'
 else:
-    django = 'django>=1.8.10,<3.0'
+    django = 'django>=2.0,<3.2'  # checked https://docs.djangoproject.com/en/dev/releases/3.1/#backwards-incompatible-3-1
 
 requirements = [
     django,