Support execution as unprivileged user? #144

Hi there,

This is exactly what I was looking for - however, I am trying to run (all of) my gameservers in Kubernetes. Depending on the cluster configuration, you may not even be able to run a container as root. Ideally, you would be able to run the containers with a securityContext enforcing an unprivileged uid. In situations like these, gosu will fail outright.

I think this can be as easy as wrapping exec gosu usage in various places with a function call that basically does:

if [ -z $NO_GOSU ]; then
  exec gosu ...
else
  raw_command
fi

I am happy to submit a PR but wanted to get thoughts on adding this before doing it.

Thanks!