fix various bugs

this pull request:

- adds `object` mode, which is `{"rows": []}` (returning arrays to certain versions of IE exposes a json parsing security vulnerability)
- fixes all modes to work when the database is empty. previous `newline` mode returned `\nundefined` and `array` mode returned `]`
- adds ability to pass in default options for `SLEEPStream` to the `SLEEP` constructor
- emits errors on the sleep client stream (this was broken)