Add Django classifiers

Author: moshthepitt

setup.py

@@ -38,5 +38,10 @@
     classifiers=[
         "Programming Language :: Python",
         "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
+        "Framework :: Django",
+        "Framework :: Django :: 2.0",
+        "Framework :: Django :: 2.1",
+        "Framework :: Django :: 2.2",
     ],
 )