ingress: Add manifest for ingress-nginx

This manifest deploys the *ingress-nginx* controller, which is
responsible for handing traffic from clients outside the cluster and
routing it to the proper pods.  I am using host network mode here to
avoid having to have another proxy in front of the ingress controller,
which would be required in NodePort mode.

I looked at MetalLB briefly, but decided to avoid it for now.  As with
everything else in the Kubernetes world, it seems massively complex.

ingress/README.md

@@ -0,0 +1,15 @@
+# Ingress Setup
+
+## Deploy *ingress-nginx*
+
+Using *ingress-nginx* in [host network mode][0].  Assign the *ingress* custom
+role to nodes that will handle incoming traffic (e.g. have DNS names pointed to
+their addresses)
+
+```sh
+kubectl label node k8s-amd64-n{0,1,2}.pyrocufflink.blue kubernetes.io/role=ingress
+kubectl apply -f ingress-nginx.yaml
+```
+
+[0]: https://kubernetes.github.io/ingress-nginx/deploy/baremetal/#via-the-host-network
+