tpsrunner exposes ginkgomon interface

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Wait for a nats connection before starting

* use natsclientrunner to retry connections
* heartbeater now takes a nats client

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>