Initial stab at monitoring_check::cluster

initial stab at cluster check, just need to know if i'm going in right direction?
You asked if you could just set the source in `sensu-extra`. 

You could, but it would produce weird side effects.

Lets say this is your time line:

0:00
ServerA: locks Emits return 2
ServerB: doesn't lock. emits 0?

0:01
ServerA: doesn't lock. Emits 0?
ServerB: locks. Emits 2

0:02 Recovery
ServerA: locks. Emits 0
ServerB: doesn't lock, emits 0.

Sensu server sees:
2,0,2,0,0,0

When it should have seen:
2,2,0

All sorts of thresholds are messed up here.

I'm pretty sure the only way to sanely feed sensu the events is to do it yourself, localhost:3030.