Adding package.json for consumption via npmjs

This should get published via NPM so that people in the node world may easily consume this.

This package.json could do more, but I wanted to keep it sparse.  Set version to a `beta` so that when 1.0 is locked down, the package can be updated.
Or just `"markdown", "md", "html", "markup"`, as those four are the most popular it seems for markdown parsers on npm.