Upgrade pyasn1 to 0.2.3

[fabaff]

0.2.3

• Changelog: https://github.com/etingof/pyasn1/blob/master/CHANGES.rst#revision-023-released-25-02-2017

Tested with the following configuration:

notify:
  - platform: xmpp
    name: jabber
    sender: home@jabber-bay.org
    password: !secret xmpp_password
    recipient: home-castle@swissjabber.org

[mention-bot]

@fabaff, thanks for your PR! By analyzing the history of the files in this pull request, we identified @MartinHjelmare, @balloob and @rmkraus to be potential reviewers.