Use of toggle is expensive

[edwh]

This is on v1.1.2. When you render a model view, you call toggle to make sure that it's shown/hidden correctly based on any filter. My profiling on Chrome suggests that this is a bit of a performance hog, and you only really need to do it if the filter has indicated that you should hide it. Putting an if speeds things up a bit.

            if (hideThisModelView) {
                if( thisModelViewWrapped.children().length === 1 )
                    thisModelViewWrapped.toggle( ! hideThisModelView );
                else modelView.$el.toggle( ! hideThisModelView );
            }