Document get_converging_lines #9
Description
Document function get_converging_lines https://github.com/perellonieto/PyCalib/blob/master/pycalib/visualisations/ternary.py#L154 with the same standard than accuracy https://github.com/perellonieto/PyCalib/blob/master/pycalib/metrics.py#L8 and others including a couple of simple doctests.