Migrate to reticulate

[TomKellyGenetics]

@jonathonshor @adamgayoso
Due to difficulties reproducing this package in R. It will be migrated to calling the Python functions in R, using the “reticulate” package provided by RStudio.

This has the main benefit of calling exactly the same functions as the current version of the Python implementation. It will be convenient for R users but have the drawbacks of dependancy on the Python version (requiring it be installed) and slower performance from passing data between R and Python.

I’ve already got this to run successfully for another Python module: https://github.com/TomKellyGenetics/leiden