Traverse ancestors in DOM to find clientWidth for responsive images

We have an `<img>` tag whose parent is an `<a>` tag. In the `cloudinary_update` function, it attempts to retrieve the `clientWidth` based on the immediate parent (see [here](https://github.com/cloudinary/cloudinary_js/blob/master/js/jquery.cloudinary.js#L552-L555)). Since our immediate parent is an `<a>` tag, this results in 0 which exits out early. We added logic to traverse up the DOM to grab the ancestor's `clientWidth`.

Note: the other parts of the diff are trailing whitespace fixes.