amp-add-class throws error with SVG elements in IE 10

[daver208]

amp-add-class includes amp-has-class which appears to be based off of JQuery. When using amp-add-class on an SVGElement (or any object derived from one), the method hasClass() fails.

This because of the following line.
var cName = (isString(el) ? el : el.className).replace(whitespaceRE, ' ');
Once it sees that the element is an object it tries to use className which doesn't work for SVG Elements in IE10.

A workaround is to simply use element.classList.add('classname') and element.classList.remove('classname'). Again this was only tested in an IE 10 browser in a Windows 8 environment, testing in chrome and firefox

(edited 0516PM EST) "testing in chrome and firefox" did not have this issue, sorry for that.