Add Python3.8 in the setup.py classifiers

Author: Theofilos Manitaras

setup.py

@@ -23,6 +23,7 @@
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
+        'Programming Language :: Python :: 3.8',
         'License :: OSI Approved :: BSD License',
         'Operating System :: MacOS',
         'Operating System :: POSIX :: Linux',