Ensure that .kube/config is written once microk8s is active

[addyess]

Overview

Addresses regression from #82 raised in #84

since sg no longer is running commands, we can't use the shell redirects it used to employ -- one such redirect was for writing the .kube/config out to a file.

Details

• Created a checkOutput method to more easily capture output from stdout
• created a microk8sKubeConfig method to capture output from a exec_as_microk8s call and write to a file
• add an integration test to confirm that kubectl works out of the box

[addyess]

@deusebio would you try this branch in your repo and see if this resolves your issues?