Document support for Django 2.2.

Author: carltongibson

README.md

@@ -56,7 +56,7 @@ There is a live example API for testing purposes, [available here][sandbox].
 # Requirements
 
 * Python (2.7, 3.4, 3.5, 3.6, 3.7)
-* Django (1.11, 2.0, 2.1)
+* Django (1.11, 2.0, 2.1, 2.2)
 
 We **highly recommend** and only officially support the latest patch release of
 each Python and Django series.

docs/index.md

@@ -87,7 +87,7 @@ continued development by **[signing up for a paid plan][funding]**.
 REST framework requires the following:
 
 * Python (2.7, 3.4, 3.5, 3.6, 3.7)
-* Django (1.11, 2.0, 2.1)
+* Django (1.11, 2.0, 2.1, 2.2)
 
 We **highly recommend** and only officially support the latest patch release of
 each Python and Django series.

setup.py

@@ -61,6 +61,7 @@ def get_version(package):
         'Framework :: Django :: 1.11',
         'Framework :: Django :: 2.0',
         'Framework :: Django :: 2.1',
+        'Framework :: Django :: 2.2',
         'Intended Audience :: Developers',
         'License :: OSI Approved :: BSD License',
         'Operating System :: OS Independent',