We talked a bit about the backend for api.scheme.org with Arthur, and
came to the conclusion that SRFI 176/168 would be a good implementation
strategy.

Can you recommend a simple key-value store to use as the engine?

- LevelDB from Google seems simple and widely available; the only
problem is that it doesn't have transactions and we'd have to write our
own transaction layer.

- FoundationDB looks very fancy - but probably _too_ fancy. We don't
need to have a distributed system for such a simple application.

An in-process library similar to SQLite could be the ideal choice.
LevelDB seems like it would fit the bill, except for transactions.