Add Python static type linting via mypy Coala bear

Can use mypy, a statically typed version of Python, to add static type linting. Something like (from home-assistant):

[testenv:typing]
basepython = python3
deps = -r

/requirements_test.txt
commands = mypy --silent-imports homeassistant

or mypy coala bear:

https://github.com/coala/coala-bears/blob/master/bears/python/MypyBear.py