Added API parameters for user and password

This is my first attempt at adding the capability of setting the API username and password.

The use of types for configuring sensu is a little advanced for me, but I think I got it right.

It does have an unexpected (to me) behavior of not removing the api_user and api_password from the json when you remove the parameters. I guess this is a side effect of how the provider is implemented? May I ask, why not just use an erb?

I don't understand the build failures though. They seem to be unrelated to my changes? And I seem to get them, even when I run against the upstream master?

I've also set the sensitive config files to 440.