An example demonstrating the use of rxjava and how it can be leveraged to create a stream of sensor data that can be subscribed to.
Dagger is used to inject a singleton type "service" which
provides access to the Ambient Light Sensor. LightSensorService has a Subject that
can be subscribed to by calling LightSensorService#subscribeToSensor().
AmbientLightFragment subscribes to the service and displays the raw value reported
from the sensor.