Support multiple files in KUBECONFIG env variable

[drubin]

According to the official docs we should be able to load multiple config files and join them.

The client currently doesn't support this we should support it.

References comment in #226 (comment)

[brendandburns]

fwiw, the merging rules here are really poorly defined, but we can take a rough stab and see what compatability things people complain about...

[drubin]

@starpit this has been merged it would be really nice if you could give it a test see if it works for you? Let us know if you manage to give it a test

You should be able to reference it before its published via the npm GitHub style includes https://docs.npmjs.com/files/package.json#repository