Update setup.py

Add py3.6, py3.7, py3.8, py3.9 support

Author: achapkowski

setup.py

@@ -21,11 +21,13 @@
         'Environment :: Win32 (MS Windows)',
         'Intended Audience :: Developers',
         'License :: OSI Approved :: Apache Software License',
-        'Programming Language :: Python :: 2',
-        'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
         'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
+        'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
+        'Programming Language :: Python :: 3.8',
+        'Programming Language :: Python :: 3.9',
         'Programming Language :: Python',
     ],
     description='This package allows for Single-Sign On HTTP Negotiate authentication using the requests library on Windows.',