add goodbye event to server model, regenerate code.
reintroduce test for goodbye/goodbye-ok.
Merge pull request #37 from mknoszlig/master

Problem: goodbye event is not considered in server model
regenerate code with latest zproto version.
adapt clojure tests to account for zproto changes.
Merge pull request #38 from mknoszlig/master

Problem: generated code is behind current zproto version