Add support for appropriate GOMAXPROCS that's aware of Kubernetes limits.

[patrickdappollonio]

When http-server is run with Kubernetes resource requests/limits, the limits seen by the container are not the same limits set in the resources: section. It's a longstanding issue in the Go community where on a CFS scheduler, Go mistakenly takes the value of the host not the value provided by CFS.

This is a very simple change that imports Uber's gomaxprocs package which automatically configures these values if they're running inside container with a CFS scheduler.