delete method
Deletes all records, or a specific record.
Implementation
Future<dynamic> delete(String thing) {
final id = _generateId();
final completer = Completer();
wait().then((_) {
once(id, (res) => _output(res, 'delete', thing, completer));
_send(id, 'delete', [thing]);
});
return completer.future;
}