misc: list Python 3.6 (sic!) in setup.py.

This is a "bump" commit to force CircleCI picking up the new
branch.

Python 3.6 is known-to-work and regularly tested; it missing in
setup.py is an oversight.

Python 3.7 is not yet known to work, is just starting to get one
module tested, - therefore not adding it here (yet).

Author: veox

setup.py

@@ -115,6 +115,7 @@
         'License :: OSI Approved :: MIT License',
         'Natural Language :: English',
         'Programming Language :: Python :: 3.5',
+        'Programming Language :: Python :: 3.6',
     ],
     # trinity
     entry_points={