Fix autobahn dependencies
Fix autobahn dependencies

Upstream is having some dependency trouble:

   https://github.com/crossbario/autobahn-testsuite/issues/55

Lock txaio to 2.1.x for now.

Note that the unittest2 requirement is now correctly included in
upstream, so that hack has been removed.

jchampio/apache-websocket,jchampio/apache-websocket,jchampio/apache-websocket