flutter pub upgrade (#178)

provider_shopper/lib/main.dart

@@ -22,13 +22,13 @@ class MyApp extends StatelessWidget {
       providers: [
         // In this sample app, CatalogModel never changes, so a simple Provider
         // is sufficient.
-        Provider(builder: (context) => CatalogModel()),
+        Provider(create: (context) => CatalogModel()),
         // CartModel is implemented as a ChangeNotifier, which calls for the use
         // of ChangeNotifierProvider. Moreover, CartModel depends
         // on CatalogModel, so a ProxyProvider is needed.
         ChangeNotifierProxyProvider<CatalogModel, CartModel>(
-          initialBuilder: (context) => CartModel.empty(),
-          builder: (context, catalog, previousCart) =>
+          create: (context) => CartModel.empty(),
+          update: (context, catalog, previousCart) =>
               CartModel(catalog, previousCart),
         ),
       ],

provider_shopper/pubspec.lock

@@ -115,7 +115,7 @@ packages:
       name: provider
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "3.1.0+1"
+    version: "3.2.0"
   quiver:
     dependency: transitive
     description: