Add a preview image.
Update some of the text to reflect current status.
Add the maintainers.
Move installation instructions to a separate file, since the README has become unweildy.
Add a description of the versioning system.

I didn't know how this would work when we first started, but it's
settled down now so worth writing it out.
I always like seeing alternatives when I view other projects.
Add a script that takes a yaml file and converts it to a JSON file

Requires PyYAML. If this dependency is an issue on a particular
platform, pretty much any language allows you to do this.

A ruby example is

    ruby -ryaml -rjson -e 'puts JSON.pretty_generate(YAML.load(ARGF))' < project.yml > project.json