Update unit of measurement within integration (#171)

Device API operates in Celsius regardless of config otherwise

custom_components/gree/climate.py

@@ -157,7 +157,7 @@ def __init__(self, hass, name, ip_addr, port, mac_addr, timeout, target_temp_ste
 
         self._target_temperature = None
         self._target_temperature_step = target_temp_step
-        self._unit_of_measurement = hass.config.units.temperature_unit
+        self._unit_of_measurement = '°C'
 
         self._current_temperature = None
         self._temp_sensor_entity_id = temp_sensor_entity_id