#1435 Proxy the view's el on the behavior in addition to $el

To address @jmeas's [concerns](https://github.com/marionettejs/backbone.marionette/issues/1435#issuecomment-45174398), Backbone.View  only creates a new `el` if one isn't provided at construction (`_ensureElement`). 
I think we can also add another `it` in one of the tests that's using `$el` to make sure that the `el` works the way it should.