Returning collectionView on renderCollection().

To make it possible to track your model views of your collections. It is very handy to have a reference to the collectionView. Currently you can only use a syntax like this._subviews[1].views but this is rather hacky, nor do you exactly know what view it is.

By giving renderCollection() a return value of collectionView you can easily do 
this.views = this.renderCollection();
_.each(this.views, function(view){});