Adding skel examples

Thoughts about adding basic examples for the spark widgets library? PR is incomplete wanted to test the waters before finishing it up.

Also noticed a dependency in `spark-icon-button.html` that should be a bindable or default to a base64 encoded object for shipping.   

```
           /* TODO: Should btn_light be bindable? */
            background-image: url("images/btn_light.png");
```

@ussuri @terrylucas