Geosketch

https://github.com/brianhie/geosketch/pull/19

Updates to new sklearn API from https://github.com/brianhie/geosketch/pull/10

In v0.24 sklearn.cluster.k_means_ was deprecated so it's been changed to sklearn.cluster._kmeans in kmeanspp.py.

Additional minor fixes:

- fixed method name in reduce_dimensionality error message
- removed old scanpy.api interface in favor of just scanpy
- bumped geosketch version to 1.2

- Return 1-indexed result for R interface

- Change default number of covering boxes (without replacement) to desired sketch size.
- More even sampling from covering boxes.
- Add parameter documentation.
- Additional improvements.

- Bug fix in k-means++ function