css binding doesn't work with class names with slashes, etc. in 2.2

See https://groups.google.com/d/topic/knockoutjs/5TLU9hqEqtE/discussion

Previously we had been able to use complex css class names in the css binding, like so

```
<div class="box" data-bind="css: { 'complex/className' : someBoolean() }">
    Dom element with breaking binding
</div>​
```

[Fiddle (2.1, working)](http://jsfiddle.net/allen/MRAx3/)

Now, the class name that is applied is `complex className`

[Fiddle (2.2, not working)](http://jsfiddle.net/allen/MRAx3/1/)