Remove unneeded comparator

This collection is just an in-memory indexer used for typeaheads. For
display, the matching models are added to a separate collection. Thus,
the order of the elements in the typeahead collection does not matter.

js/views/new_conversation_view.js

@@ -24,10 +24,6 @@ var Whisper = Whisper || {};
       storeName: 'conversations',
       model: Whisper.Conversation,
 
-      comparator: function(m) {
-          return m.get('name');
-      },
-
       _tokenize: function(s) {
           s = $.trim(s);
           if (s.length === 0) {