[fix bug 956712] Add missing required class in registration's optin checkbox.
[fix bug 956734] Remove <h1> and </h1> from page title.
Merge pull request #756 from glogiotatidis/956712

[fix bug 956712] Add missing required class in registration's optin chec...
Merge pull request #757 from glogiotatidis/curatedgroups

[fix bug 956734] Remove <h1> and </h1> from page title.
Bug 951840 - Send members of curated groups emails upon changes

Changes from review:

* Use .get(q) instead of .filter(q).get()
* Change join_group to always add the logged-in user.
* Remove special privileges for superusers in joining and leaving groups.
* Change how we track which membership requests we've sent reminders for.
  Now keep timestamps on the group for when the last request was received,
  and when the last reminder was sent.
* Don't import from deprecated django.conf.urls.defaults.
* Add quotation marks around group names in emails.

Fix bug 951840