setup.py and requirements.txt have inconsistent dependencies

[BrenBarn]

setup.py requires scikit-learn>=0.20,<0.21dev0 while the requirements.txt lists scikit-learn>=0.21,<0.23dev0, which appear to be mutually exclusive. It looks like the latter was updated recently while the former has not been updated for a year and a half.

[BenjaminBossan]

Thanks for the heads up

[BenjaminBossan]

#41