setup.py: Small updates for Python 3

Author: cmcqueen

setup.py

@@ -1,12 +1,8 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 import sys
 
-try:
-    from setuptools import setup, Extension
-except ImportError:
-    from distutils.core import setup
-    from distutils.extension import Extension
+from setuptools import setup, Extension
 
 import _version
 
@@ -52,6 +48,8 @@
         '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',
         'Topic :: Communications',
     ],
 )