Mapbox key and map ID have been removed. You'll have to add your own if you want to see the examples working.
Mapbox.js: https://www.mapbox.com/mapbox.js/api/v2.1.0/
Leaflet: http://leafletjs.com/
AngularJS: https://angularjs.org/
angular-leaflet-directive: https://github.com/tombatossals/angular-leaflet-directive
X-Tag: http://x-tag.org/
Polymer: https://www.polymer-project.org/
RequireJS: http://requirejs.org/
Component Kitchen (search for "maps"): http://component.kitchen/
Custom Elements on html5rocks.com: http://www.html5rocks.com/en/tutorials/webcomponents/customelements/