#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`). 
What kind of behavior do you think should be tested? I was thinking that if Backbone.View creates the proper `el`, then this `el` should be good.