brew install skaffold

Proposing to add `brew install skaffold` installation method to README

Author: cedricvidal

README.adoc

@@ -81,6 +81,7 @@ You will need the following components to get started with Skaffold:
       -  `curl -Lo skaffold https://storage.googleapis.com/skaffold/releases/latest/skaffold-linux-amd64 && chmod +x skaffold && sudo mv skaffold /usr/local/bin`
    -  To download the latest OSX build, run:
       -  `curl -Lo skaffold https://storage.googleapis.com/skaffold/releases/latest/skaffold-darwin-amd64 && chmod +x skaffold && sudo mv skaffold /usr/local/bin`
+      - if using `homebrew`, you can `brew install skaffold`
 
 . Kubernetes Cluster
    -  link:https://kubernetes.io/docs/tasks/tools/install-minikube/[Minikube],