Switch to multi-platform release build

Update build-release to match latest state of openshift/origin. It now uses a docker image to create releases for mac(darwin), win, and linux(amd64)
Copy the dockerfile :)

----- Original Message -----
> > @@ -0,0 +1,25 @@
> > +# This file creates a standard build environment for building STI
> 
> This is to build multi-platform sti releases (not necessarily inside origin)
> 
> ---
> Reply to this email directly or view it on GitHub:
> https://github.com/openshift/source-to-image/pull/72/files#r19363395