remove go-simple-db references from go-slog

- ref: https://github.com/GigaOM/legacy-pro/issues/3806
- particularly this [comment](https://github.com/GigaOM/legacy-pro/issues/3806#issuecomment-49641387)
- accompanying config: https://github.com/GigaOM/gigaom/pull/4903

Since the window of time that we can fetch with `go-loggly` is so small, perhaps a shorter date would be appropriate in order to conserve screen real estate?  Perhaps:

```php
'loggly_date'     => date( 'M j, H:i:s', $value->timestamp / 1000 ),
```