Make new event-bus the default

[flosell]

#144 introduced a new event-bus that should resolve deadlock issues with the old implementation. It is currently an opt-in feature. Once we got feedback from some production users, make this the new default

[MediaMarco]

Our biggest pipeline runs with lambdacd 0.13.0 and the new eventbus since 10 days. Looks good. We ran into deadlocks with the old eventbus.

[flosell]

@MediaMarco Thanks for the feedback!