Clean up README / description.md

[orblivion]

• [x] Before release: I have some stuff I need to clean up the README and description.md, I have local TODOs for this stuff.
• [x] After release: Reflect that it's been released. This will soon not be an "experimental" or "in progress" app. And fix the link to the demo accordingly. Perhaps remove some references to "goals" as well, depending on what they are.