Sending emails to newly-accepted attendees sends them to ALL accepted attendees

[williln]

Just realized that when I accepted some attendees from the waitlist, then emailed them through the Messaging app, it emailed ALL accepted attendees, resulting in duplicate email notifications. It would be nice to have a way to email newly accepted people, and ignore folks who've already received the email.

Or set a second drop-down to skip people who've RSVP's, at least.

[burhan]

How about https://github.com/DjangoGirls/djangogirls/pull/313