Add subject_template_name argument

With Django 1.4, the signature for ``PasswordResetForm.save`` added a
``subject_template_name`` argument using templates for the password
reset email subject rather than hard-coding the string.  Our
``CustomContextPasswordResetForm.save`` method needs to take this
argument as well.

Closes #661
Merge branch 'hotfix-661-reset_password' into develop

Conflicts:
	README.rst
Merge remote-tracking branch 'origin/develop' into 426-child_promoting_theme
Refine section landing page template

Renamed the ``teaser`` placeholder to be ``description`` to
better reflect @jwirfs-brock's
[comment](https://github.com/PitonFoundation/atlas/issues/426#issuecomment-14180196)
about how the content on these pages is structured.

I also adjusted the grid system classes to make the list of sub-pages
align correctly.

Addresses #426