[bug 1074276] Remove abuse classification prototype

This removes the abuse classification infrastructure. It was temporary
code that we were using to test abuse classification with the spicedham
system. We've gathered our data. Thus we remove this infrastructure
while we plan for the next round.
Merge pull request #353 from willkg/1074276-remove-spicedham

[bug 1074276] Remove abuse classification prototype
Update django-nose to v1.2
Update docs re REUSE_DB
Remove selenium

The smoketest suite uses selenium, but the unit test suite does not.
Thus we can remove selenium from vendor/packages and the requirements
file that the unit test suite uses.
Update peep and codify --no-use-wheel

After working on bug #1074861 (peep issue #50), I decided we shouldn't use
wheels for now. The crux of the issue is that if you have a github-tarball
based requirement and then switch to a pypi based requirement which
downloads a wheel, then pip doesn't clean things up properly and you end
up with cruft in your virtual environment which includes .py, .pyc and
metadata files. Ew.

Further Mike and Dean said they've had instances where peep downloads a
wheel and then a non-wheel, so you need to have both hashes in the
requirements file. Ew.

Because of these two issues, it's easier to not do wheels. So I updated
peep to the latest and then modified it so it's always passing
--no-use-wheel to pip.

I also fixed the shas in the requirements file that were for wheels.

Plus when testing all of this, I had a problem where the vagrant
provisioning script was creating /root/.pip and dying with a permission
issue. So I fixed that, too.

* https://bugzilla.mozilla.org/show_bug.cgi?id=1074861
* https://github.com/erikrose/peep/issues/50
[bug 1075563] Fix missing flake8 issue

In the conventions chapter, we suggest that the developer use the
pre-commit hook we have to lint code before it gets committed. However,
we needed to tell the developer to install flake8 first.

This fixes that.