Add Python 3.8 classifier (Netflix#38)

Author: abdullahselek

setup.py

@@ -390,6 +390,7 @@ def run(self):
         "Intended Audience :: Developers",
         "License :: OSI Approved :: Apache",
         "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.8",
     ],
     package_dir={"": "src"},
     packages=find_packages("src"),