devel/py-pystorm: add support to build py36 FLAVOR
Makefile - adopt this port; - msgpack is no longer a dependency for 3.1.4 (7d7dac6, and ece1f00); - check PYTHON_MAJOR_VERSION before adding dependencies. files/* - patch setup.py in order that readme() works with py36.
Approved by: araujo (mentor)
Differential Revision: https://reviews.freebsd.org/D18822