Load fixtures.body() as DOM

[Ryuno-Ki]

For traversal etc. I think, it would be handy to have the ability to load content as DOM.

Therefore, I extended your API to realise that.

PR coming soon.

[Ryuno-Ki]

See #28.

After walking through the specs, the following code seem to work, too:

fixtures.load('some.html');
var iFrameWindow = fixtures.window();
var content = iFramWindow.document.body.children();

The content variable looks like I would like to have. What about creating a function for it?