Advertise python3.5 support

For now we don't break compability with python3.5, so why not advertise
it!

setup.py

@@ -34,6 +34,7 @@ setup(
         'Programming Language :: Python :: 2',
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
+        'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',