Platform support policy proposal

There is a fair amount of confusion about the specific operating system platforms, platform versions, etc. that Chef Software, Inc. supports for its products. This RFC will clarify this by calling out the individual operating systems and their releases as explicitly supported or not.
> So very :-1: on CVT testers for RHEL variants. And even :-1: on omnibus testers for chef-client for RHEL variants, but :+1: on Tier 1 support for them (and Amazon as well -- which is a pure-cloud distro so jenkins testers gets complicated there unless we patch in test-kitchen).

Surely I'm wrong in what I am saying, but if you are talking about tests using vagrant, it may be easier to use [vargrant-aws](https://github.com/mitchellh/vagrant-aws) in the CI instead of integrating tests with test-kitchen.