Update project meta data

- Bump copyright years
- Add Python 3 and Python 3.7 trove classifiers

setup.py

@@ -1,6 +1,6 @@
 #
 # gvacommon - common parts of gnuviechadmin
-# Copyright (C) 2016-2018  Jan Dittberner
+# Copyright (C) 2016-2020  Jan Dittberner
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License as published by
@@ -38,7 +38,8 @@ setup(
     classifiers=[
         'Development Status :: 4 - Beta',
         'License :: OSI Approved :: GNU Affero General Public License v3 or later (AGPLv3+)',
-        'Programming Language :: Python',
+        'Programming Language :: Python 3',
+        'Programming Language :: Python 3.7',
         'Intended Audience :: Developers',
     ],
     keywords='gnuviechadmin',