Add Python 3 and CPython classifiers

Author: hroncok

setup.py

@@ -120,6 +120,10 @@ def libraries(self, value):
           'Programming Language :: Python',
           'Programming Language :: Python :: 2',
           'Programming Language :: Python :: 2.7',
+          'Programming Language :: Python :: 3',
+          'Programming Language :: Python :: 3.5',
+          'Programming Language :: Python :: 3.6',
+          'Programming Language :: Python :: Implementation :: CPython',
           'Topic :: Software Development :: Libraries',
           'Topic :: System :: Networking',
       ],