hCalendar tags

Embedded [hCalendar](http://microformats.org/wiki/hcalendar) data in the main event content as a (quick, simple) alternative to the iCal feed.  I had to make a minor wording tweak to get the "summary" property, which is required.

There has been [some critisism](http://www.webstandards.org/2007/04/27/haccessibility/) of the use of `abbr` tags in this way.

Feedback requested.