fix bug 1047020 - Add Wheel Hashes to Requirements

Pins pep8 at 1.5.7 (The current tarball hash), and adds hashes for pep8 and pyflakes wheels.

Fixes bug 1047020
The peep [docs](https://github.com/erikrose/peep/blob/master/README.rst#old-pypi-roulette) explain why even if you have an explicit version, how you can get different package types from PyPI.