output a css structure object

[leeoniya]

personally, i author static stylesheets as js objects and use https://github.com/cssobj/cssobj to compile them (which handles a basic level of optimizations). since DropCSS already tokenizes the css (besides properties), it would be useful to expose the tokens to allow the build-out of a small post-processor which completes the parsing of props and creates a js object that can be fed into cssobj for final optimizations & compression.

probably the only actionable thing for this lib is to return the css tokens alongside the generated css.