Minimax protoclust method

[instantkaffee]

The prototype minimax linkage method for hierarchical clustering is a popular method as it resembles nice practical properties:

http://faculty.marshall.usc.edu/jacob-bien/papers/jasa2011minimax.pdf

Its implemented by protoclust R package:

https://cran.r-project.org/web/packages/protoclust/index.html

Request to add method to tidyclust.