After observing errors from importing our iCal into Outlook, I found
there were a few issues with our generated output according to [0].
This adds an overall VERSION to the iCal and sets per event timestamps
and UIDs.
This also updates YAML loading to use safe_load to get rid of a
deprecation warning noticed while testing.
[0] https://icalendar.org/validator.html?url=https://releases.openstack.org/schedule.ics
Change-Id: I3803a432da2538af4de163b77c192130366ddadf
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>