TST: added test for automatically find the center and the rings
TST: added test for automatically find the center and the rings

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