shouldHave error when asserting prop type attributes

[dereke]

When doing something like this:

monkey.find('script').shouldHave({
  attributes: {async: true}
})

against this:

<script async></script>

The test fails. I think this is because some attributes are actually properties.
So I wonder for these if we should have something like:

monkey.find('script').shouldHave({
  properties: ['async']
})