DEV: add function to define energy range of a spectrum
DEV: add function to define energy range of a spectrum

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