Take attendees out of google event sync

When someone picks a calendar to sync to other than their default, adding attendees causes
it to show up on their default calendar as well.  This commit removes all attendees from
the event.
@twinge While this commit fixes the issue of an event being added to multiple calendars, I'm wondering if this aspect of the code was necessary or not.  I would assume that the event summary should take care of the contacts involved, but if this was here for a reason, I could throw the comments in the event description instead.  Thoughts?