Update tests from 'nose' to 'pytest'
Update tests from 'nose' to 'pytest'

Nikea/scikit-xray,scikit-xray/scikit-xray,scikit-xray/scikit-xray,tacaswell/scikit-beam,tacaswell/scikit-xray,tacaswell/scikit-xray,Nikea/scikit-xray,Nikea/scikit-xray,tacaswell/scikit-beam,scikit-xray/scikit-xray,tacaswell/scikit-beam,tacaswell/scikit-xray