don't cast F2C conversion to int

[aesthetic]

prevents rounding errors that show the wrong emoji when displaying temp as Celsius

[kpengboy]

Have you tested to make sure that this doesn't display 10 digits of (unwanted) precision when someone requests a temperature in Celsius? EDIT: nvm second inspection shows it wouldn't happen

On a larger note though, I think the organization of code in this module is flawed and bug-prone. IMO icon should require the caller to pass Fahrenheit temperatures, and color should convert Celsius to Fahrenheit before figuring out which bucket the temperature belongs in.

[kpengboy]

I would prefer the methodology of PR #154. (In any case though, thanks for the contribution.)