Feature Request: Support Celsius

[michaelfavia]

Thanks for a great system. I'd really appreciate Celsius support.

The easiest way i see is to base the set value off of:
temperaturescale: https://developer.nest.com/documentation/api-reference/overview#temperaturescale

Then the system would react to whatever the user specified from their nest instead of requiring you to store that info.

If you point me in the right direction id be happy to to take a shot at this myself.

Python Temp Conversion:

Celsius = (Fahrenheit - 32) * 5.0/9.0
Fahrenheit = 9.0/5.0 * Celsius + 32