0install blog draft

This pull request is to track the 0install blog post. Notes:

1. It's currently blocked on getting the DNS entry added, so you can't follow along currently. We need this entry added:

   tools.ocaml.org -> CNAME ocaml.github.io

2. The easiest way to see the images seems to be to symlink them into the root locally.
Should we mention this? 0install works on Windows, but OPAM doesn't I think.