Second round of reviews

Update preface. We're on Phase III now.

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Spatial Data course

Chapters 3 and 4 used for a workshop on spatial data in Leeds.

Spatial tidyverse

This version was presented at Geocomputation 2017, Leeds, alongside a workshop on the spatial tidyverse.

10 page sf tutorial

This is a 10 page tutorial on sf - the beginnings of a book.