Sync _.isFinite changes with Underscore and update vendor/underscore and vendor/backbone.

Former-commit-id: 9acb93a276a11da8186da76bd82f1fd6f89c27dd

vendor/backbone/test/router.js

@@ -481,4 +481,15 @@ $(document).ready(function() {
     });
   });
 
+  test("#1746 - Router allows empty route.", 1, function() {
+    var Router = Backbone.Router.extend({
+      routes: {'': 'empty'},
+      empty: function(){},
+      route: function(route){
+        strictEqual(route, '');
+      }
+    });
+    new Router;
+  });
+
 });