support reading tar files as configs

[cristifalcas]

This is a feature request.

Add the possibility to give to skaffold an yaml file with the skaffold.yaml file and any additional files needed in requirements, or rawyamls

I think that the support should be only in untar-ing the archive somewhere and selecting the skaffold.yaml file from that folder.

This will make it easy to package all requirements in one file that we can keep locally, or in GCS