Drop support for Python 3.5, add Python 3.9 (#75)

Author: emlaver

setup.py

@@ -79,10 +79,10 @@ def finalize_options(self):
       classifiers=[
           'Programming Language :: Python',
           'Programming Language :: Python :: 3',
-          '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'
           'Development Status :: 4 - Beta',
           'Intended Audience :: Developers',
           'License :: OSI Approved :: Apache Software License',