allow arrays for boolean attribute and classes

Closes #5.

As I was doing this I thought...

What if any string value could also be an array? I think it should be consistent, so if we're not sold on it for all possible types, I don't think we should merge it just for these two (`booleanClass`, `booleanAttribute`).

So as an example, this would work:

```js
'model.key': {
    type: 'toggle',
    yes: ['#true_case', '#another_true_case']
    no: '#false_case'
}
```