add "cancelled" and newsflash to ical feed

[ionous]

google calendar doesn't indicated canceled events well, so this prepends it to the ride title. this also adds the newsflash, since that's often part of canceling; ( and therefore fixes #723 )

for example, the feed for https://www.shift2bikes.org/calendar/event-19594 now looks like:

UID:[email protected]
SUMMARY:CANCELLED: The Stark Street Swooper: Ventura to Multnomah Falls
via Dabney, Corbett, and Vista House
DESCRIPTION:Excessive Heat Ride to Far to risk any lives, Moved over to
next week let\nJoin us at 9:30AM for this exhilarating ride starting at

the bold parts are new.

( note: the newsflash here "correctly" ends with the word "let" -- it matches the text on the website. maybe user error, or more likely clipped on input/storage to the db? doesn't affect this issue tho. )

[carrythebanner]

@ionous You're right, there is a bug in handling the newsflash (filed that as #800). This PR shouldn't have any effect on that so we can still merge this.