Updates to new sklearn API from #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

Bump to version 1.0

• 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

Initial release of geometric sketching implementation