Doesn't support RECURRENCE-ID or EXDATE

[mbalfour]

The basic RRULE command is implemented, but not the companion RECURRENCE-ID or EXDATE commands:
https://nylas.com/blog/rrules/

If you have an ics file that looks like this:
BEGIN:VEVENT
UID:0000001
RRULE:FREQ=DAILY;COUNT=5
SUMMARY:Treasure Hunting
DTSTART;TZID=America/Los_Angeles:20150706T120000
DTEND;TZID=America/Los_Angeles:20150706T130000
END:VEVENT

BEGIN:VEVENT
UID:0000001
SUMMARY:Treasure Hunting
LOCATION:The other island
DTSTART;TZID=America/Los_Angeles:20150707T120000
DTEND;TZID=America/Los_Angeles:20150707T130000
RECURRENCE-ID;TZID=America/Los_Angeles:20150707T120000
END:VEVENT

Right now, ical.js will silently replace the recurring event with the single instance. This happens where the code does this:
if (curr.uid)
par[curr.uid] = curr

This should probably look something more like this:
if (curr.uid)
{
if (par[curr.uid] === undefined)
{
par[curr.uid] = curr
}
else
{
// TODO: Add support for RECURRENCE-ID
}
}

Neither the old behaviour or this one is correct, but if you added error-handling code at the TODO area, you could warn users when the calendar is being parsed incorrectly.

[thomkrillis]

It seems this should have been resolved by #64. Can this issue be closed?