remove self dependency in the requirement and add openpyxl
remove self dependency in the requirement and add openpyxl

making new tests highlight a missing dependency
scikit-rf/scikit-rf,jhillairet/scikit-rf,temmeand/scikit-rf,temmeand/scikit-rf,temmeand/scikit-rf,scikit-rf/scikit-rf,jhillairet/scikit-rf,jhillairet/scikit-rf