[FEATURE] toggle log/non-log in repr?

[lukasheinrich]

maybe this is asking to much from a simple repr and just a matter of just plottting the hist properly.. but while integrating hist in pylhe I wondered whether some smart heuristic looking at min()/max() counts could be used to decide whether to show logarithmic y-axes (e.g. if smalles non-zero entry and larges entry are many orders of magnitude apart?)

https://nbviewer.jupyter.org/github/scikit-hep/pylhe/blob/master/examples/awkward_example.ipynb