Fixed Nginx and updated Consul image

[misterbisson]

• replaced containerpilot.json with co-process and telemetry
• changed Nginx health check URL to more specific path to reduce likelihood of conflicts
• update Consul image to https://github.com/autopilotpattern/consul
• add build notes

If merged, it should be tagged as 4.5.3-r2.

[tgross]

LGTM except for my concerns in https://github.com/autopilotpattern/nginx/pull/18#discussion_r71872292