README.MD lacking a few things which are good to know when it comes to using/installing Helm Broker

[mszostok]

Description

Current documentation lacking a few things which are good to know when it comes to using/installing Helm Broker:

• In prerequisites section we do not specify the concrete version of required tools (you cannot always install the newest one because we do not support that)

• We do not specify for which k8s version Helm Broker works (e.g. we still do not support K8s 1.16 release)

• The installation process should be more precise on how to run minikube and how to init helm. Currently, user will get a problem with minikube installation because minikube start is not everything that needs to be set. Same thing for helm init . Suggestion: use kind instead of minikube.

  Add info that you need to clone our repo to be able to install Helm Broker chart,

  # install Service Catalog
  $helm install svc-cat/catalog --name catalog --namespace catalog
  
  # install Helm Broker
  helm install charts/helm-broker --name helm-broker --namespace helm-broker
  

  as you can see, commands are the same, but in the first case, it will work because the remote repo holds SeviceCatalog chart. In case of Helm Broker you need to have that chart locally.

  [stretch goal] Add option to install Helm Broker from remote repo

• Specify the concrete version of required tools in run-tests section

• create a devguide document with project structure and purpose of our directories (e.g. what should be put in /pkg, /hack etc. some things I've already commented in this PR description )