fix(router): respond to hashchange events

Previously if the URL changed in `HashLocation` mode, the router would not pick up the change.
This adds a listener in `HashLocationStrategy` for `hashchange` events to fix the problem.

Closes #5013

tools/broccoli/trees/browser_tree.ts

@@ -43,6 +43,7 @@ const kServedPaths = [
   'playground/src/person_management',
   'playground/src/order_management',
   'playground/src/gestures',
+  'playground/src/hash_routing',
   'playground/src/hello_world',
   'playground/src/http',
   'playground/src/jsonp',