Add django 2.2 support

Author: monouno

pg_partitioning/__init__.py

@@ -1,7 +1,7 @@
 """
 A Django extension that supports PostgreSQL 11 time ranges and list partitioning.
 """
-REQUIRED_DJANGO_VERSION = [(2, 0), (2, 1)]
+REQUIRED_DJANGO_VERSION = [(2, 0), (3, 0)]
 DJANGO_VERSION_ERROR = "django-pg-partitioning isn't available on the currently installed version of Django."
 
 try:

setup.py

@@ -28,7 +28,7 @@ def rel(*xs):
 
 extra_dependencies = {
     "django": [
-        "Django>=2.0,<2.2"
+        "Django>=2.0,<3.0"
     ],
 }