altimeter_to_station_pressure documentation errors

[jrleeman]

What can be better?

1. The sentence This function is useful for working with METARs since they do not provide altimeter values, but not sea-level pressure or station pressure. should read This function is useful for working with METARs since they provide altimeter values, but not sea-level pressure or station pressure.

2. There is a math error in the equation explanation (see attached)