The problem was that unsubscribe re-added the doc to the connection.
Now the doc is removed from the connection after unsubscribe.
Additionally, we're no longer waiting for the unsubscribe response
before executing the callback. It is consistent with Query,
unsubscribe can't fail anyway and the subscribed state is updated
synchronously on the client side.

See See https://github.com/nodejs/Release

See See https://github.com/nodejs/Release

I had to add the --exit flag workaround to mocha.opts to make it exit
when tests are done. A better long-term solution would be to ensure
that nothing keeps node running after all tests are done, see
https://boneskull.com/mocha-v4-nears-release/#mochawontforceexit.

The problem was that unsubscribe re-added the doc to the connection.
Now the doc is removed from the connection after unsubscribe.
Additionally, we're no longer waiting for the unsubscribe response
before executing the callback. It is consistent with Query,
unsubscribe can't fail anyway and the subscribed state is updated
synchronously on the client side.

The issue could not cause problems in practice because
ot-json0 does not support presence.

See share#219