Start using hacking 0.6

So we can start using new hacking 0.6 checks.

Since hacking 0.6 pins pep8, pyflakes and flake8 they can be removed
from test-requires. For any unfixed checks list them in tox.ini

Fix a H103, 'Header does not match Apache 2.0 License notice' that
leaked in

Change-Id: I652fe3270f1c37afdd386bfae7c4b27b6abcfa06

test-requirements.txt

@@ -1,9 +1,4 @@
-# Install bounded pep8/pyflakes first, then let flake8 install
-pep8==1.4.5
-pyflakes==0.7.2
-flake8==2.0
-hacking>=0.5.3,<0.6
-
+hacking>=0.5.6,<0.7
 coverage>=3.6
 discover
 feedparser