dest needs to be outside of options

If `dest` is under options, Grunt reads it as `options.dest` and you get this error:

```bash
Running "esri_slurp:dev" (esri_slurp) task
Warning: Cannot read property 'dest' of undefined Use --force to continue.

Aborted due to warnings.
```

In order to be read as `files.dest` it has to be at the root of the target.