Updates samples for latest beta release of the Flutter SDK (#492)

* Updating for beta release

* Re-adding pub get to Flutter travis script

add_to_app/flutter_module_books/pubspec.lock

@@ -14,7 +14,7 @@ packages:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.4.1"
+    version: "2.4.2"
   boolean_selector:
     dependency: transitive
     description:
@@ -22,6 +22,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "2.0.0"
+  characters:
+    dependency: transitive
+    description:
+      name: characters
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.0"
   charcode:
     dependency: transitive
     description:
@@ -42,7 +49,7 @@ packages:
       name: collection
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.14.12"
+    version: "1.14.13"
   fake_async:
     dependency: transitive
     description:
@@ -66,7 +73,7 @@ packages:
       name: matcher
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.12.6"
+    version: "0.12.8"
   meta:
     dependency: transitive
     description:
@@ -113,7 +120,7 @@ packages:
       name: stack_trace
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.9.3"
+    version: "1.9.5"
   stream_channel:
     dependency: transitive
     description:
@@ -141,14 +148,14 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.16"
+    version: "0.2.17"
   typed_data:
     dependency: transitive
     description:
       name: typed_data
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.1.6"
+    version: "1.2.0"
   vector_math:
     dependency: transitive
     description:
@@ -157,4 +164,4 @@ packages:
     source: hosted
     version: "2.0.8"
 sdks:
-  dart: ">=2.7.0 <3.0.0"
+  dart: ">=2.9.0-14.0.dev <3.0.0"