Adds isNodeAttached helper method.

PR 1 for `onAttach`

This adds a helper method `isNodeAttached`. It lets you know if an element is a child of the document or not. I also updated `triggerDOMRefresh` to take advantage of the new helper.
ok so this prob seems crazy but...

I think we should stub Backbone.$.contains
and only test that this method returns a boolean...

otherwise we are just writing tests for jquery :(