Pull request to enable display of barometric pressure

[stavefan]

Modification of code and readme that permits display of the barometric pressure.

[mtatsuma]

Thank you for your PR.

Could you provide a sample picture that the pressure is enabled?

I'm concerned about the visibility because the pressure graph may overwrap the other graph (e.g. rain and temperature).

[stavefan]

Attached is a screenshot

[mtatsuma]

I'll create a new release after I test it on my environment.