Support Django 2.2 (#346)

README.rst

@@ -14,7 +14,7 @@ Generate **real** Swagger/OpenAPI 2.0 specifications from a Django Rest Framewor
 Compatible with
 
 - **Django Rest Framework**: 3.7.7, 3.8, 3.9
-- **Django**: 1.11, 2.0, 2.1
+- **Django**: 1.11, 2.0, 2.1, 2.2
 - **Python**: 2.7, 3.4, 3.5, 3.6, 3.7
 
 Only the latest patch version of each ``major.minor`` series of Python, Django and Django REST Framework is supported.

setup.py

@@ -57,6 +57,7 @@ def drf_yasg_setup(**kwargs):
             'Framework :: Django :: 1.11',
             'Framework :: Django :: 2.0',
             'Framework :: Django :: 2.1',
+            'Framework :: Django :: 2.2',
             'Topic :: Documentation',
             'Topic :: Software Development :: Code Generators',
         ],

tox.ini

@@ -8,6 +8,7 @@ envlist =
     py{27,34,35,36}-django111-drf{37,38,39},
     py{34,35,36,37}-django20-drf{37,38,39},
     py{35,36,37}-django21-drf{37,38,39},
+    py{35,36,37}-django22-drf{37,38,39},
     djmaster, lint, docs
 
 [testenv:.package]
@@ -19,6 +20,7 @@ deps =
     django111: Django>=1.11,<2.0
     django20: Django>=2.0,<2.1
     django21: Django>=2.1,<2.2
+    django22: Django>=2.2,<2.3
 
     drf37: djangorestframework>=3.7.7,<3.8
     drf38: djangorestframework>=3.8.0,<3.9