This makes a few key changes to test runs in an effort to avoid a few

types of warnings and failures on newer versions of Python and Django,

and when the network is down.
We now disable the smart mail spoofing on test runs, avoiding DNS

lookups any time fake e-mail is being sent. We also now avoid loading

extensions unnecessarily on each test run.
Django 2.0 deprecation warnings are now filtered out on test runs,

avoiding a lot of unwanted noise.
We also now override the nose options to avoid doing doctests, which

triggered an error inspecting some non-UTF-8 data files during test

runs.

Unit tests pass on Python 2.7/Django 1.6 and Python 3.7/Django 1.11.
Tested Review Board and extension tests.