Slabdip

Generate new figures in notebooks in line with upcoming publication.

What's Changed
* Neural network by brmather in https://github.com/brmather/Slab-Dip/pull/2


**Full Changelog**: https://github.com/brmather/Slab-Dip/compare/v3.0...v4.0

Replaced the simple linear formulation with a K nearest neighbour implementation.
Also created the `SlabDipper` object and package installation

- Updated slab dip formation in response to reviews.
- Simplified notebook by using `gplately` API