[WIP] helper for comparing histograms

[schmitts]

I've added a helper class to compare "stuff" and a concrete implementation for comparing histograms, as well as an example. The expected output is attached. I'm aware that it needs some work, but before I go into polishing I'd like to discuss if you find it helpful in the first place.

[pwaller]

This looks pretty great. I note that the branch is called WIP_compare, is there anything which is waiting?

[ndawe]

Yeah, thanks for this extremely useful feature! I'll review.

[ndawe]

Just add the doc text here like the other examples and print __doc__. This is used in the automatic documentation generation.

[schmitts]

This looks pretty great. I note that the branch is called WIP_compare, is there anything which is waiting?

Documentation for sure. Feature wise I'm not sure. I'm migrating my
plotting scripts at the moment, so whenever I hit a feature that's not
in yet, I'll add it.

[schmitts]

I made some changes to the implementation. I couldn't put it in plottings.utils because of circular dependencies when import Legend.

[ndawe]

What about separating this PR into two components: one part in a new module plotting.layout that could contain a highly configurable RatioPlot class (and more to come in the future) and then a separate module plotting.compare that would make use of RatioPlot?