Add initial version of analytics and crash reporting package.

pkg/telemetry/README.md

+# telemetry
+
+A library to facilitate reporting analytics and crash reports.
+
+## Analytics
+
+This library is designed to allow all Dart SDK tools to easily send analytics
+information and crash reports. The tools share a common setting to configure
+sending analytics data. To use this library for a specific tool:
+
+```
+import 'package:telemtry/telemtry.dart';
+import 'package:usage/usage.dart';
+
+main() async {
+  final String myAppTrackingID = ...;
+  final String myAppName = ...;
+
+  Analytics analytics = createAnalyticsInstance(myAppTrackingID, myAppName);
+  ...
+  analytics.sendScreenView('home');
+  ...
+  await analytics.waitForLastPing();
+}
+```
+
+The analytics object reads from the correct user configuration file
+automatically without any additional configuration. Analytics will not be sent
+if the user has opted-out.
+
+## Crash reporting
+
+To use the crash reporting functionality, import `crash_reporting.dart`, and
+create a new `CrashReportSender` instance:
+
+```dart
+import 'package:telemtry/crash_reporting.dart';
+
+main() {
+  Analytics analytics = ...;
+  CrashReportSender sender = new CrashReportSender(analytics);
+  try {
+    ...
+  } catch (e, st) {
+    sender.sendReport(e, st);
+  }
+}
+```
+
+Crash reports will only be sent if the cooresponding [Analytics] object is
+configured to send analytics.