docs: update link to learning promises

to the chapter in Dr. Axel Rauschmayer's ES6 book from his old post
closes #1005

The old link on the documentation lead to an article on promises that
contained outdated information, so this one leads to newer content.

public/docs/ts/latest/guide/architecture.jade

@@ -403,7 +403,7 @@ figure
   Here's an example of a service class that logs to the browser console
 +makeExample('architecture/ts/app/logger.service.ts', 'class', 'app/logger.service.ts (class only)')(format=".")
 :marked
-  Here's a `HeroService` that fetches heroes and returns them in a resolved [promise](http://www.2ality.com/2014/10/es6-promises-api.html). 
+  Here's a `HeroService` that fetches heroes and returns them in a resolved [promise](http://exploringjs.com/es6/ch_promises.html). 
   The `HeroService` depends on the `LoggerService` and another `BackendService` that handles the server communication grunt work.
 +makeExample('architecture/ts/app/hero.service.ts', 'class', 'app/hero.service.ts (class only)')(format=".")
 :marked

public/docs/ts/latest/guide/router.jade

@@ -966,7 +966,7 @@ code-example(format="").
 :marked
   The `DialogService` (injected in the `AppComponent` for app-wide use) does the asking.
   
-  It returns a [promise](http://www.2ality.com/2014/10/es6-promises-api.html) that
+  It returns a [promise](http://exploringjs.com/es6/ch_promises.html) that
   *resolves* when the user eventually decides what to do: either
   to discard changes and navigate away (`true`) or to preserve the pending changes and stay in the crisis editor (`false`).
 

public/docs/ts/latest/tutorial/toh-pt4.jade

@@ -288,7 +288,7 @@ code-example(format="." language="html").
   It does that work (somewhere) and eventually it calls our function with the results of the work or an error.
 .l-sub-section
   :marked
-    We are simplifying. Learn about ES2015 Promises [here](http://www.2ality.com/2014/10/es6-promises-api.html) and elsewhere on the web.
+    We are simplifying. Learn about ES2015 Promises [here](http://exploringjs.com/es6/ch_promises.html) and elsewhere on the web.
 :marked
   Update the `HeroService` with this promise-returning `getHeroes` method:
 +makeExample('toh-4/ts/app/hero.service.ts', 'get-heroes', 'hero.service.ts (getHeroes)')(format=".")