Specify version requirements for dependencies

[ejhigson]

When I tried running the example at https://sherbold.github.io/autorank/ I got an attribute error:

AttributeError: module 'scipy.stats' has no attribute 'median_absolute_deviation'

I was running scipy v1.1.0. Upgrading scipy to 1.4.1 fixed the issue. Perhaps you can consider specifying minimum version requirements for your dependencies in setup.py? E.g. "scipy>=1.4" or whatever the appropriate version is.