Add default values to print_valid_kwargs()

[rmatsum836]

Is your feature request related to a problem? Please describe.
I was just looking through inp_functions.py to find the default values for several kwargs, and I think it would be nice to add these to the doctoring that is printed from print_valid_kwargs().

Describe the solution you'd like
For kwargs that have default values, such as coord_freq, add the default values to the doc string for print_valid_kwargs().

Describe alternatives you've considered
Maybe this is information is already present somewhere else that I'm missing.

[rsdefever]

They are here: https://mosdef-cassandra.readthedocs.io/en/latest/guides/kwargs.html

But I am not opposed to adding them to print_valid_kwargs as well.