Support static files with LiveServerTestCase.

Change the Django 1.7 dependencies in the tox.ini so they pull from
pypi rather than the builds on www.djangoproject.com
Removing note about the toolbar being unmaintained.
Ignore flake8 warnings for has_key in cache panel.

Ignore flake8 warnings for has_key call in cache panel because we need to support caches that may still use it.