Remove await in front of self.async_write_ha_state() calls

[Chupaka]

Adjustment as discussed in #152

[ScratMan]

Unfortunately, I can't test by myself, temperature is already high. Could someone validate the behaviour?
It looks a bit strange the name of the function starts with async_ while it's not defined as an asynchronous function.

If it's working correctly I will make a new release.

[ScratMan]

My test environment crashed, I lost its config and need to rebuild it from scratch.
I reviewed the code, and it uses the same method usage as other methods that were already working fine, so I'm going to release it.