.grayscale-off class not preserved by JS Polyfill

[voltaek]

In the tabbed interface I'm using this library for, one of the tabs is active by default, and therefore the image is not grayed-out. However, when the JS polyfill makes its pass in IE on page load, the .grayscale-off class is stripped and not placed onto the div that wraps the svg element, so even the active tab ends up with a grayed-out image.

I see that you preserve the .grayscale-fade class, can you also please support preserving the .grayscale-off class?