isort + checkstyle pre-commit hooks now on master

[Brian Wickman <wi...@apache.org>]

I highly recommend you copy build-support/hooks/pre-commit to
.git/hooks/pre-commit on a freshly pulled master.  This will enable python
import order checking and now rudimentary style checking on each commit.

Both are broken on master now but I will be submitting subsequent reviews
to fix them.  You can skip the checking with SKIP_AURORA_HOOKS=1.  It would
be great to see these run server side in the future, but for now we can
self-police on an opt-in basis.

~brian