Use pip -e in setup_develop

We have some complex logic in here to try to do the right things with
the requirements before doing the install of the package which still
winds up being wrong in some cases. Since having written this code,
we've learned that the logic we're trying to achieve is actually what
pip install -e does. So just use that. We have to follow up with a chown
of the resulting egg-info directory, because the sudo command will cause
it to be written by root, which prevents subsequent commands from
operating without privilege in the directory.

Change-Id: I7454f0053c36b15051b616363a5fc04c0045b57c