Clean up config.yml

[mnlevy1981]

I don't think we use data_sources.sname any more, and there might be other unnecessary variables in the file as well. (We used to write output to computed_notebooks/{sname}/ but dropped that extra directory in #153

[mnlevy1981]

It looks like we've removed sname from examples/key_metrics/config.yml, but we haven't updated the documentation. Also, maybe we can add nb_path_root and run_dir as command-line arguments to cupid-diagnostics and drop the data_sources section entirely?

[dsanders02]

@mnlevy1981 were you hoping to remove the values run_dir and nb_path_root or use xml variables from CESM workflow?

[mnlevy1981]

@dsanders02 We don't need to add these to the xml file right now, it's hard to think of a situation where a user would want to use a non-standard nblibrary or run dir as part of the CESM Workflow. I just want the option to run

$ cupid-diagnostics --run-dir /path/to/run_dir --nblibrary-dir /path/to/nblibrary

with default values of . for --run-dir and ../../nblibrary for --nblibrary-dir and then we can remove a few lines of code from the config.yml files:

################
# Data Sources #
################
data_sources:
    # run_dir is the path to the folder you want
    ### all the files associated with this configuration
    ### to be created in
    run_dir: .

    # nb_path_root is the path to the folder that cupid will
    ### look for your template notebooks in. It doesn't have to
    ### be inside run_dir, or be specific to this project, as
    ### long as the notebooks are there
    nb_path_root: ../../nblibrary

[TeaganKing]

Hey @mnlevy1981 and @dsanders02 -- I am thinking that it would also be possible that someone running standalone CUPiD (eg, not part of the CESM workflow) would want to use a different nb_path_root. So, maybe we do want to keep this in the config file? Thoughts?