Bootstrap / Component setup async (#6264)

* Bootstrap / Entiy setup async

* Cleanup add_job stuff / return task/future object

* Address paulus comments / part 1

* fix install pip

* Cleanup bootstrap / move config stuff to config.py

* Make demo async

* Further bootstrap improvement

* Address Martin's comments

* Fix initial tests

* Fix final tests

* Fix bug with prepare loader

* Remove no longer needed things

* Log error when invalid config

* More cleanup

* Cleanups platform events & fix lint

* Use a non blocking add_entities callback for platform

* Fix Autoamtion is setup befor entity is ready

* Better automation fix

* Address paulus comments

* Typo

* fix lint

* rename functions

* fix tests

* fix test

* change exceptions

* fix spell

homeassistant/components/sensor/mqtt_room.py

@@ -59,7 +59,7 @@ MQTT_PAYLOAD = vol.Schema(vol.All(json.loads, vol.Schema({
 @asyncio.coroutine
 def async_setup_platform(hass, config, async_add_devices, discovery_info=None):
     """Setup MQTT Sensor."""
-    yield from async_add_devices([MQTTRoomSensor(
+    async_add_devices([MQTTRoomSensor(
         config.get(CONF_NAME),
         config.get(CONF_STATE_TOPIC),
         config.get(CONF_DEVICE_ID),