Proofreading documentation and tutorials

[g4brielvs]

This PR is for proofreading documentation and tutorials. Verify (and fix if needed) notebooks for reproducibility.

[bpstewar]

I have updated and trimmed the tutorial notebooks; they work for me now and have working data in the data folder.

[elbeejay]

@bpstewar can you provide data sources / places where data should be downloaded for many of these functions and notebooks? It isn't clear to me where the data in the data folder comes from. Many of the functions (as well as examples in the implementations notebooks) rely on a lot of geospatial datasets.