Update to ResponsiveImage to trigger and emit "error" if an image is not found.

Build fix.

Update to ```ResponsiveImage``` to trigger and emit "error" if an image is not found; provides the ability to bind a callback on error. Example use case:

```
var responsiveImage = ResponsiveImage['createFromElement'](imageElement);
    responsiveImage['on']('load', onLoadCallback);
    responsiveImage['on']('error', onErrorCalback);
```