Example authentication

When I first tried the tutorial I found myself at a loss as to how to specify the auth params ([ZeroCloud Authentication Config](https://zerovm.readthedocs.org/projects/zerovm-zpm/en/latest/zerocloud-auth-config.html) was several clicks away) and what values to use for the params. Some examples makes it much more clear.
Merge pull request #28 from everett-toews/patch-1

Add example authentication to zebra tutorial