Rename Navigator 2.0 to Router (#712)

* Rename Navigator 2.0 to Router

This aligns better with the documentation for this new API, and doesn't
imply that apps need to be upgraded.

* introduction -> navigator

navigation_and_routing/README.md

@@ -1,49 +1,47 @@
 # Navigation and Routing sample code
 
 Sample code for [Learning Flutter's New Navigation and Routing System][article],
-an article explaining Navigator 2.0.
+an article explaining the Router widget and it's associated classes.
 
 ## Samples
 
-**Navigator 1.0 samples**
+**Navigator samples**
 
-* [nav_1/anonymous_routes.dart](lib/nav_1/anonymous_routes.dart) - Shows how to
-  use a Navigator to push and pop anonymous routes (e.g. MaterialPageRoute)
-* [nav_1/named_routes.dart](lib/nav_1/named_routes.dart) - Shows how to use
-  define named routes via the `routes` parameter on MaterialApp, and navigate
-  using Navigator.pushNamed
-* [nav_1/on_generate_route.dart](lib/nav_1/on_generate_route.dart) - Shows how
-  to handle arbitrary named routes using the `onGenerateRoute` callback defined
-  in the `MaterialApp` constructor.
+* [navigator/anonymous_routes.dart](lib/navigator/anonymous_routes.dart) -
+  Shows how to use a Navigator to push and pop anonymous routes (e.g.
+  MaterialPageRoute)
+* [navigator/named_routes.dart](lib/navigator/named_routes.dart) - Shows
+  how to use define named routes via the `routes` parameter on MaterialApp, and
+  navigate using Navigator.pushNamed
+* [navigator/on_generate_route.dart](lib/navigator/on_generate_route.dart) -
+  Shows how to handle arbitrary named routes using the `onGenerateRoute`
+  callback defined in the `MaterialApp` constructor.
 
-**Navigator 2.0 samples**
+**Router samples**
 
-* [nav_2/pages.dart](lib/nav_2/pages.dart) - Shows how to define a list of
+* [router/pages.dart](lib/router/pages.dart) - Shows how to define a list of
   [Page] objects on Navigator declaratively.
-* [nav_2/router.dart](lib/nav_2/router.dart) - Full sample that shows a custom
+* [router/router.dart](lib/router/router.dart) - Full sample that shows a custom
   RouteInformationParser and RouterDelegate parsing named routes and
   declaratively building the stack of pages for the Navigator.
 
-
 **Advanced**
 
-* [nav_2_advanced/nested_router.dart](lib/nav_2_advanced/nested_router.dart) -
+* [router_advanced/nested_router.dart](lib/router_advanced/nested_router.dart) -
   Shows two [RouterDelegate], one nested within the other. A
   [BottomNavigationBar] can be used to select the route of the outer
   RouterDelegate, and additional routes can be pushed onto the inner
   RouterDelegate / Navigator.
-* [nav_2_advanced/transition_delegate.dart](lib/nav_2_advanced/transition_delegate.dart)
+* [router_advanced/transition_delegate.dart](lib/router_advanced/transition_delegate.dart)
   Shows how a custom TransitionDelegate can be used to customized when
   transition animations are shown.
 
-
 ## Running
 
 Each file in this project is an entrypoint. To run, specify the filename of
 the sample:
 
 ```bash
-flutter run lib/nav_2/router.dart
+flutter run lib/router/router.dart
 ```
-
 [article]: https://medium.com/flutter/learning-flutters-new-navigation-and-routing-system-7c9068155ade

navigation_and_routing/lib/router_advanced/transition_delegate.dart

@@ -5,7 +5,7 @@
 /// Shows how a custom TransitionDelegate can be used to customized when
 /// transition animations are shown. (For example, [when two routes are popped
 /// off the stack](https://github.com/flutter/flutter/issues/12146), however the
-/// default TransitionDelegate will handle this if you are using Navigator 2.0)
+/// default TransitionDelegate will handle this if you are using Router)
 import 'package:flutter/material.dart';
 
 void main() {