Log warning using async_write_ha_state

[albertinizao]

Is your feature request related to a problem? Please describe.
I see a warning recurrent log

WARNING (Dummy-15) [homeassistant.helpers.frame] Detected that custom integration 'hon' calls async_write_ha_state from a thread other than the event loop, which may cause Home Assistant to crash or data to corrupt. For more information, see https://developers.home-assistant.io/docs/asyncio_thread_safety/#async_write_ha_state at custom_components/hon/sensor.py, line 849: self.async_write_ha_state(), please report it to the author of the 'hon' custom integration

[kubasaw]

MQTT message handler is running in separated thread, so this warning occur every time message is received.

I'm fixing this (and much more issues) in fork, but at the moment it is quite unstable: https://github.com/IoTLabs-pl/hon