Add Prometheus to monitor applications

[visola]

Description

Add the Prometheus server to the cluster and get it to publish metrics to Google Stackdriver. Start here: https://cloud.google.com/monitoring/kubernetes-engine/prometheus

Acceptance Criteria

• When the environment is created in GCP, it includes a Prometheus server
• Metrics published to Prometheus get piped to Stackdriver and can be easily visualized
• Instructions on how to visualize metric in Stackdriver are added to the README