Fix activation email typo.

It looks like there used to be some pluralization logic once upon a time, but
it got removed (presumably for a good reason).

I've no idea where `expiration_days` gets set (it doesn't seem to occur
anywhere other than this file), but on the actual site right now it's set to 7.
And 7 is plural, so saying "7 day" is wrong and awkward.  Now it's not wrong or
awkward.
Add registration link to login page.

The log in link is available on every page, but if you go there and don't have
an account, you previously had no easy way to create one.

Ideally, these should be on the same page, so we can reuse the username and
password (both as form elements and as things the user may have already filled
in).  This stuff is all handled by django-registration, though, and I don't
want to go hacking about in there.

So, we just leave a link below the login form redirecting to the registration
page, which should be Good Enough.
Update footer copyright.

The project has gotten a fair amount of work since 2010 (from some 66 different
people!), so update the footer to reflect that.  We don't want people to think
rtfd is dead!
Merge pull request #427 from xiongchiamiov/update-copyright-year

Update footer copyright.
Small style fix.
Merge pull request #426 from xiongchiamiov/add-registration-link-to-login-page

Add registration link to login page.
Merge pull request #424 from xiongchiamiov/activation-email-typo

Fix activation email typo.
Update dnspython
Add updated lb config
Update app nginx config
Add rest-framework plumbing.
Add CORS support.
Move settings to proper place.
Initial attempt at parsing a .rtd.json file in repos.
Initial attempt at supporting deprecation of versions.
Add distlib to requirements
Add notification endpoints
Add metrics page
Upgrade Django
correct background url attribute to prevent 404 for #version_menu li a selector