Update various examples to use the Mapbox v4-API

examples/reusable-source.html

@@ -4,6 +4,9 @@ title: Reusable Source
 shortdesc: Updating a tile source by changing the URL.
 docs: >
   You can call <code>source.setUrl()</code> to update the URL for a tile source.  Note that when you change the URL for a tile source, existing tiles will not be replaced until new tiles are loaded.  If you are interested instead in clearing currently rendered tiles, you can call the <code>source.refresh()</code> method.  Alternatively, you can use two separate sources if you want to remove rendered tiles and start over loading new tiles.
+cloak:
+  - key: pk.eyJ1IjoiYWhvY2V2YXIiLCJhIjoiY2pzbmg0Nmk5MGF5NzQzbzRnbDNoeHJrbiJ9.7_-_gL8ur7ZtEiNwRfCy7Q
+    value: Your Mapbox access token from https://mapbox.com/ here
 ---
 <div id="map" class="map"></div>
 <button class="switcher" value="0">January</button>