Copy array of waiting descents before continuing.

Closes #116.
Tidy `package.json`.
Fix broken `package.json`.
Add `bugs` property to `package.json`.
Checksum is not both algorithm and stored size.

Making space for the binary leaf page implementation. Eventually, we
need the checksum algorithm to implement `crypto.Hash` as a stream as
well, so that our checksum function actually just builds a new instance
of a checksum stream.

See #105.
Resurrect `checkJSONSize`.