add python 3.8 to support list

Author: jnozsc

setup.py

@@ -41,6 +41,7 @@
         "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.8",
         "Programming Language :: Python",
         "Topic :: Internet :: Proxy Servers",
         "Topic :: Internet",