Link to Edit List view for checklists the user created.
Update dependency for newer version of django-registration.
Update custom backend for new django-registration version.

The new version of django-registration uses class-based views, and no
longer requires overriding a "Backend" class, as one can simply pass the
registration form override to the RegistrationView class.
Update django-recaptcha to version 0.0.6.
Create a custom registration form with a captcha field.

The django-recaptcha project no longer depends directly on
django-registration and no longer provides a registration form for us,
so we just need to create one ourselves based on the prior one.
Fix #447 - Registration fails on signup.

This fix is the actual source of the error, but the registration system
needed to be updated for Django 1.5, so we went ahead and updated
django-registration and django-recaptcha to newer versions anyway.
Hide the Checklist "Share" button until we implement it.