Temperature updates should be more frequent

[dawiinci]

@mouth4war mentioned in this thread that the update is quicker when the App is opened.

https://github.com/rytilahti/python-miio/issues/577#issuecomment-587330632

I also get the temperature updates every 0.5 °C which is pointless. Wouldn't it be possible to do the same as the app and refresh more often? This might also help with the fan going offline intermittently - as described in the link above.