Initial version of HAProxy controller

[jcmoraisjr]

A very first, but fully functional, initial version of HAProxy controller.

[k8s-reviewable]

This change is 

[bprashanth]

I think haproxy is popular enough that we can take this, but in general I want to push users to keeping controllers in their tree, though, per: https://github.com/kubernetes/ingress/tree/master/docs/faq#how-do-i-contribute-a-backend-to-the-generic-ingress-controller

[bprashanth]

People will surely ask for caddy and/or envoy next. I'm on the fence, where do we draw the line? @jcmoraisjr how hard would it be to maintain this in your tree and add examples, as indicated in the faq linked above.

[jcmoraisjr]

@bprashanth I read the faq a while ago and really missed the how to contribute a backend part, sorry. No problem, I think I can maintain this controller in my own fork and update some common pages here as you have indicated.

[coveralls]

Coverage increased (+0.04%) to 44.249% when pulling 5f73b61 on jcmoraisjr:jm-haproxy into 1cebef2 on kubernetes:master.

[bprashanth]

Thanks so much for the pr!
Please link into https://github.com/kubernetes/ingress/blob/master/docs/catalog.md and add examples, since a lot of people have asked for a haproxy controller. I've filed #215 and I'm closing this for now. You shouldn't need to fork, just vendor ingress as a godep?