Upgrade to Django 1.7

Note that I've switched to using pip to install.  For some reason,
`python setup.py install` causes `django-admin` and `django-admin.py` to
be installed incorrectly.  Switching to pip fixes that, though I'm not
sure why.
Merge pull request #173 from tswicegood/upgrade/django-1.7

Upgrade to Django 1.7