Updated khal to 0.8.4.

0.8.4
=====
released 2016-10-06

* **IMPORTANT BUGFIX** fixed a bug that lead to imported events being
  erroneously shifted if they had a timezone identifier that wasn't an Olson
  database identifier. All users are advised to upgrade as soon as possible. To
  see if you are affected by this and how to resolve any issues, please see the
  release announcement (khal/doc/source/news/khal084.rst or
  http://lostpackets.de/khal/news/khal084.html). Thanks to Wayne Werner for
  finding and reporting this bug.

(wiz)