Fixed an issue where `site.domain` returned 127.0.0.1 rather than the URL in the email subject and template.  This is an issue when running uwsgi/Gunicorn behind a proxy server like Nginx.  Now we allow `site.domain` to be obtained  from the database value first (if it exists) then from the url if it doesn't.
Fixing a commit I overwrote.  I restored Honi's changes from here: https://github.com/brutasse/django-password-reset/commit/79ffe3556e5650d59a66b7ce59033778b703ca60.
get_site() documentation.
Merge pull request #19 from dereknutile/master

Site.domain returns 127.0.0.1 behind Nginx