Suggestion: change names of event #16

Because Polymer event (set in sortablejs.html) have the same name as in the native Sortable library,
a Polymer listener function would be called twice. What I usually do is to process the function only when event.detail exists :

listeners : {
  'sortable.add': 'onSortableAdd'
},

onSortableAdd: function(e) {
console.info('called twice');
if(e.detail) {
   doStuff
}

What about changing all event with a sortable- prefix (before too many people use this young library...)

Thanks anyway,
C.