sensor fix, readme configuration examples

custom_components/empty_sensor/README.md

@@ -0,0 +1,7 @@
+```yaml
+# example configuration:
+
+sensor:
+  - platform: empty_sensor
+    name: Empty sensor
+```

custom_components/empty_sensor/sensor.py

@@ -1,17 +1,18 @@
 import esphome.codegen as cg
 import esphome.config_validation as cv
 from esphome.components import sensor
-from esphome.const import CONF_ID
+from esphome.const import CONF_ID, UNIT_EMPTY, ICON_EMPTY
 
 empty_sensor_ns = cg.esphome_ns.namespace('empty_sensor')
 
 EmptySensor = empty_sensor_ns.class_('EmptySensor', cg.PollingComponent)
 
-CONFIG_SCHEMA = cv.Schema({
+CONFIG_SCHEMA = sensor.sensor_schema(UNIT_EMPTY, ICON_EMPTY, 1).extend({
     cv.GenerateID(): cv.declare_id(EmptySensor)
 }).extend(cv.polling_component_schema('60s'))
 
 def to_code(config):
     var = cg.new_Pvariable(config[CONF_ID])
     yield cg.register_component(var, config)
+    yield sensor.register_sensor(var, config)