Fix issues with matplotlib.hist.

For some reason mpl.hist hangs when n_bins is set to auto.

This is related with https://github.com/numpy/numpy/issues/8203

This MR set the default value to doane. Furthermore, allows you to pick one of the options here https://docs.scipy.org/doc/numpy/reference/generated/numpy.histogram.html#numpy.histogram

This will fix one of the points here bob.pad.base!43 (merged)