Update supported Python versions

Author: hugovk

setup.py

@@ -39,11 +39,15 @@
           'Intended Audience :: Developers',
           'Topic :: Software Development :: Libraries',
           'Development Status :: 5 - Production/Stable',
+          'Programming Language :: Python :: 2',
           'Programming Language :: Python :: 2.6',
           '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 :: Implementation :: PyPy',
           'License :: OSI Approved :: MIT License', ]
       )