Include supported Python versions classifiers in setup
diff --git a/setup.py b/setup.py
index 9e14132..cc5127d 100644
--- a/setup.py
+++ b/setup.py
@@ -48,6 +48,9 @@
         "Intended Audience :: Developers",
         "Programming Language :: Python",
         "Programming Language :: Python :: 3",
+        "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: Implementation :: CPython",
         "Programming Language :: Python :: Implementation :: PyPy",
         "Topic :: Internet :: WWW/HTTP :: Dynamic Content",