Update trove classification to include Python 3.6

Author: stefankoegl

setup.py

@@ -68,6 +68,7 @@
     'Programming Language :: Python :: 3.3',
     'Programming Language :: Python :: 3.4',
     'Programming Language :: Python :: 3.5',
+    'Programming Language :: Python :: 3.6',
     'Programming Language :: Python :: Implementation :: CPython',
     'Programming Language :: Python :: Implementation :: PyPy',
     'Topic :: Software Development :: Libraries',