Implement heartbeat

Closes #1 
Also mentioned IRL, but the concept of an "Interactor" isn't really like a real thing, it's more like a concept which Uncle Bob uses to give a group of things a name, these things being use-cases. This is a minor thing, but it does kinda nag me having the word `Interactor` standalone here (second opinions are welcome here).

The suggestion I have would be to find a name that's more in the realm of the problem space we're in, and that has to do with sending information to an external service. I believe a name like `Stats` might be more in tune with what this object does as it builds the stats for the external collector (Riemann) and sends it over.