v0.2.1

No code change from 0.2.0.

0.2.0's first publish attempt was interrupted: npm reported success, the registry
eventually recorded the version, but its tarball was never stored and requests for
it answer 404. Re-publishing over it is refused (E409 Cannot publish over previously staged version), so the same tree ships as 0.2.1, and npm carries a
deprecation notice on 0.2.0. Install 0.2.1 or later.