IW: Start testing

Minimal karma testing integration. 
I just don't get this syntax:

```{tile_source = sampleScene.tileSource,
                layers  = sampleScene.layers,
                styles  = sampleScene.styles,
                options = {}
           } = {}```

It looks partially like ES6 destructuring (but with an ```=``` instead of ```:```, so that can't be it), and also default arguments.