Django registration

Adds Registration through the django-registration-redux package.

Uses sample templates from django-registration-redux for now.
This leads with the uncommon case ("someone pretending to be you") and has poor grammar. 

Also it seems to be missing the actual link.

How about this wording instead:

<p>
    {% blocktrans %}
    To activate your account at {{ site.name }}, please click the following link within the next
    {{ expiration_days }} days:
    {% endblocktrans %}
    [ACTUAL LINK HERE]
</p>
<p>
    {% blocktrans %}
    If you didn't ask to register an account, please ignore this email.
    {% endblocktrans %}
</p>