This PR changes the instructions for running Prometheus and Grafana in Docker to use the `--add-host` parameter instead of the `--link` parameter which is deprecated and which has been reported by @shaunsmith to sometimes not work.
The supplied command has been verified by @shaunsmith on Mac and Linux and by me on Linux.
* Change basic stats to use opentracing rather than Prometheus API directly
* Just ran gofmt
* Extract opentracing access for metrics to common/metrics.go
* Replace quotes strings with constants where possible
* Docker stats to Prometheus
* Fix compilation error in docker_test
* Refactor docker driver Run function to wait for the container to have stopped before stopping the colleciton of statistics
* Fix go fmt errors
* Updates to sending docker stats to Prometheus
* remove new test TestWritResultImpl because we changes to support multiple waiters have been removed
* Update docker.Run to use channels not contextrs to shut down stats collector
