Documentation updates needed

[jkrasting]

A few to-dos:

• Establish a readthedocs site would be helpful with API referencing
• Ensure every function and class has a proper docstring
• Update README.md
• Add appropriate DOE and Princeton Acknowledgements

[jetesdal]

This is a useful list. Where should we start? I think that all functions have a docstring except the low-level ones. If we remove the preprocessing routine we should have description on the required naming of the input dataset. Also @gmacgilchrist's description on the calculations would be useful to include (maybe in the readthedocs)?

[jetesdal]

A simple example with MOM6 output would add a necessary step after loading the data and before initializing the swmt class: Do a xr.merge() with the variables in ds_vars and grid info in ds_static and rename to the xwmt standard (CMOR?) naming:

ds = xr.merge([ds_vars,ds_static]).drop_dims(['xq','yq']).reset_coords(drop=True).rename({'xh': 'x', 'yh': 'y','geolat': 'lat', 'geolon': 'lon'})