Adding Travis config for jsonexample. (#4)

.travis.yml

@@ -0,0 +1,27 @@
+os:
+  - linux
+sudo: false
+addons:
+  apt:
+    sources:
+      - ubuntu-toolchain-r-test
+    packages:
+      - libstdc++6
+      - fonts-droid
+git:
+  depth: 3
+env:
+  - FLUTTER_VERSION=beta
+  - FLUTTER_VERSION=dev
+matrix:
+  allow_failures:
+    - env: FLUTTER_VERSION=dev
+before_script:
+  - git clone https://github.com/flutter/flutter.git -b $FLUTTER_VERSION
+  - ./flutter/bin/flutter doctor
+  - chmod +x travis_script.sh
+script:
+  - ./travis_script.sh
+cache:
+  directories:
+    - $HOME/shared/.pub-cache

jsonexample/test/main_test.dart

@@ -5,5 +5,5 @@
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
-  testWidgets('Counter increments smoke test', (WidgetTester tester) async {});
+  test('This test always passes.', () {});
 }

travis_script.sh

@@ -0,0 +1,9 @@
+set -e
+
+echo "== Testing 'jsonexample' on Flutter's $FLUTTER_VERSION channel =="
+
+pushd jsonexample
+../flutter/bin/flutter test
+popd
+
+echo "-- Success --"