Update infrastructure to more closely match other OpenStack projects

Update infrastructure to more closely match other OpenStack projects

This patch imports nova's HACKING.rst guidelines altered for Heat.
This patch imports nova's run_pep8.sh with some minor alterations.
This patch imports nova's hacking.py extensions to pep8.

This patch places the run_pep8 logic in a separate file rather than
having it spread between tox.ini and run_tests.sh.  The HACKING.rst
requirements as well as general pep8 requirements are then enforced
with run_pep8.sh.

Avoid running once the N802 rule until dependency changelogs are
less then 50 characters.

Change-Id: If46c14668eae3cf11b8fbff46d766cc589d701aa
Fixes: Bug #1131275