Upcoming events page out of date

Martin Michlmayr

The upcoming events page at http://spdx.org/about/spdx/events is quite
out of date. I just moved all past talks from the "upcoming talks" to
the "previous talks" section and added one upcoming talk. It would be
good to talk about future events at the next general (of business)
SPDX call.

Martin Michlmayr
Open Source Program Office, Hewlett-Packard