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.
Expanding on this point, our goal is for ChefDK to be the thing that you install on your workstation to use Chef, period. I'm pretty sure we have a worthwhile chunk of user base using Arch/Gentoo/Fedora/Etc. for workstations. Do we want to add a note about how you get a new thing on this list (and how does that work)? Initially we want(ed) to keep the range of supported things pretty narrow so we can iterate quickly without spending a ton of time fixing weird platform issues, but eventually I think we need to support possibly a wider range of platforms than chef-client (but there won't be 100% overlap since some platforms are more common for workstation and some are used for servers almost exclusively).