More Descriptive README Doc

[Haoen-Cui]

@Chronocook @jameslamb Thanks for open sourcing this great project!

I read through the README file but don't think I get the purpose and typical usage of this package. It seems to me that this package contains helper functions to generate slope features based on numeric values recorded at various geo-locations.

Would you consider adding more descriptive docs? I am looking for

• a short paragraph that describes the main functionalities of the package
• a few typical usages with outputs and preferably some visuals if that helps

I think the above will help people get familiar with and adopt the package.

[bburns632]

In this readme, I would add a few lines of code to the readme to allow the example to work from any directory a user may open in their terminal.

[bburns632]

I have this in process. Will wait to submit a PR until #23 is resolved, and I can test the end to end workflow.