inconsistency in wetbulb

[HoWol76]

At the beginning of the function wetbulb there is a decision tree on whether the temperature field is in Kelvin or Degrees Celsius. But in the loop at the end of the function, there is no difference, even though a calculation is made that looks surprisingly similar to the saturation pressure, which seems to depend on this distinction.

[greensh16]

The Metpy functions have now replaced Malcolm's wetbulb function so this decision tree is no longer needed (or I guess there's an internal one in the metpy wetbulb function).