Define package version in pacakge source

moist_thermodynamics/__init__.py

 from .functions import *
 from . import constants
+
+
+__version__ = "0.5.0"

setup.cfg

 [metadata]
 name = moist_thermodynamics
-version = 0.5.0
+version = attr: moist_thermodynamics.__version__
 description = Constants and functions for the treatment of moist atmospheric thermodynamics.
 long_description = file: README.md
 license = BSD 3-Clause License