coyote buttes example is broken

If you load the `examples/coyotebuttes/index.html` example only a little bit of the terrain loads. In the console I see these error messages:

```
TypeError: json.resourceSets[0] is undefined[Learn More]
aframe-aterrain-component.js line 82 > eval:24:11
TypeError: json.resourceSets[0] is undefined[Learn More]
aframe-aterrain-component.js line 82 > eval:24:11
```