Clicking on layer triggers both map.on('click') and layer.on('click') events in 1.0 b1

When an overlay layer has an associated `'click'`event, and the map has an associated `'click'`event, clicking on the overlay layer will trigger both events. This issue did not occur in 0.7.3.

Fiddle: http://jsfiddle.net/lobitolufty/xjqdnr5p/25/
