Use and follow release process suggested by helm

[sgandon]

https://github.com/helm/charts is being deprecated and they suggest to use https://hub.helm.sh/
Helm hub suggest to use Github Pages just like this repo to provide helm charts repos.
They also suggest using a commandline for handling the releases https://github.com/helm/chart-releaser.
1/ The command line is not necessary but the idea to use the released github artifacts as binaries sources is nice cause it prevents to have the binaries stored in the gir repository (see https://github.com/unguiculus/gh-pages-helm-chart-repo-example/releases)
2/ the index of the helm chart can be kept on master but can also by placed in a specific branch (like this https://github.com/unguiculus/gh-pages-helm-chart-repo-example/tree/gh-pages)