Fix: compatibility with lmfit 0.9.13
Fix: compatibility with lmfit 0.9.13

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