Add Kubernetes 1.9 and Helm 2.8.2 support

[carlosjgp]

Fixes #121

I think I need a hand here.

This is the first time I do GoLang, I sort out all the dependencies and tests are passing but Landscaper can't retrieve Tiller version for some reason I don't understand

I'll appreciate some guidance here if you have some time

Thanks!

[carlosjgp]

By the way, this is the output I get when I ran Landscaper

https://gist.github.com/carlosjgp/65dfc17de5a759cc98265bb8d340be54

[carlosjgp]

I found the problem

Helm requires a timeout option which has no default on 2.8.2
https://github.com/kubernetes/helm/blob/v2.8.2/pkg/helm/client.go#L47

But it does have a default value on 2.9.1
https://github.com/kubernetes/helm/blob/v2.9.1/pkg/helm/client.go#L48

Now is working!

[rollulus]

Hey thanks for the help! Getting those dependencies right isn't the most fun part, much appreciated. Content looks good to me but I've been out of the loop for a while, so I'll prefer a thumbs up from another contributor (@johnhofman ?) One thing though: could you be so kind to change your commit message so that they adhere to semantic commit messages? This will keep the auto-generated change log consistent. Thanks!

[carlosjgp]

Thanks for the feedback. I'm going to amend the messages right now

[rollulus]

Thanks!