Minimize pip-installed packages

Looking for feedback on cleaning out a bunch of redundancies
in our requirements files.

Don't install a bunch of other stuff, that might hide problems
during development. If the code depends on some package that's
not in vendor, vendor-local, or requirements/compiled.txt, we
want to find out about it sooner rather than later.

It turned out that nothing in requirements/prod.txt was needed
at all - everything was already in vendor or vendor-local.

Incidentally I cleaned up bin/jenkins.sh a little so I could run it locally,
to verify that I had all the packages that Jenkins would need for testing,
and I removed some .pyc files that had been checked into vendor-local.
I can split those changes into other branches if requested.