`sklearn` dependency

Hi,

sklearn is listed as a dependency in setup.py.

I think it should be scikit-learn. scikit-learn is the official name in PyPI and in conda since a while. Right now if you do:

> pip install -e .[test]

or

> pip install -e .[loads]

it is installing this package:

https://pypi.org/project/sklearn/#files

Collecting sklearn
  Downloading sklearn-0.0.tar.gz (1.1 kB)

I can fix this if you confirm it should be scikit-learn.

KR,