Small documentation improvement: add unity

[koocotte]

Hello,

A small suggestion to improve documentation: explicit unity :

Document getHumidity() return a value between 0.0-1.0 or between 0.0-100.0, to be interpreted as a percent of humidity.

float getTemperature() returns temperature as °C or °F ?

Thanks

[RobTillaart]

Thanks for this issue, Will have a look a the documentation to see how to improve.

[RobTillaart]

Created a develop branch and a PR to improve the documentation. Also includes some other pending updates.