Add iCal feeds for the different types of events

[destos]

Could also include a master feed with all events.
https://bitbucket.org/IanLewis/django-ical/src

[jsatt]

We already have an official iCal feed via Google calendar (https://www.google.com/calendar/ical/hablm4p7eoaknvtugr91o11sv4%40group.calendar.google.com/public/basic.ics). I would recommend having something that reads from that existing feed and publishes to the site.

[destos]

@jsatt and I discussed this and we were thinking have a link on google calendar events that is able to let twd.org know which even they've selected and then redirect to the correct event on twd.org. This way we can continue to use google for calendaring.

We also may be able to drive the google calendar from events on twd.org as a possibility.