[ANN] threaded heartbeat VMs added to zeroconf

Following recent talks, I added threaded heartbeats VMs to zeroconf. 

Is weird because is not anymore “zero” conf: you need to configure the machine to accept this VM… but well, this is like that :P 

The links to use are this: 

(they are listed at http://get.pharo.org, as usual)

cheers, 

Esteban