use dewpoint function in wetbulb

[ccarouge]

The start of wetbulb function is the same as the dewpoint function. Use the function instead of replicating the code.

[HoWol76]

I made a few refactoring changes in the branch refactor, including this.

[aidanheerdegen]

At the risk of being a wet bulb, this duplicates functionality that is available in metpy

https://unidata.github.io/MetPy/latest/api/generated/metpy.calc.wet_bulb_temperature.html

https://unidata.github.io/MetPy/latest/api/generated/metpy.calc.dewpoint.html

https://unidata.github.io/MetPy/latest/api/generated/metpy.calc.relative_humidity_from_specific_humidity.html

It would be better to use well tested functions from metpy IMO

[aidanheerdegen]

Also metpy already uses pint see #2

[greensh16]

The code is now using the wet_bulb_temperture, dewpoint, and relative_humidity_from_specific_humidity functions from metpy.