Clean up examples directory

sky/examples/shell/sensor.sky

-<script>
-import '/sky/framework/shell.dart' as shell;
-import 'dart:sky';
-import 'package:sky/services/sensors/sensors.mojom.dart';
-
-class MyListener extends SensorListener {
-  int count = 0;
-
-  void onAccuracyChanged(int accuracy) {
-    print("onAccuracyChanged $accuracy");
-  }
-
-  void onSensorChanged(SensorData data) {
-    double value = data.values[0] + data.values[1] + data.values[2];
-    if (value > 40.0) {
-      document.querySelector('div').textContent =
-          "Shake count " + (count++).toString();
-    }
-  }
-
-  MyListener.unbound() {
-    stub = new SensorListenerStub.unbound()
-            ..delegate = this;
-  }
-
-  SensorListenerStub stub;
-}
-
-void main() {
-  var sensorService = new SensorServiceProxy.unbound();
-  shell.requestService(sensorService);
-
-  var listener = new MyListener.unbound();
-  sensorService.ptr.addListener(SensorType_ACCELEROMETER, listener.stub);
-  listener.stub.listen();
-}
-</script>
-<div>Shake me.</div>