This PR contains two main changes.
Python 3 support (which is required for point 2).
At some point one wants / needs to use submission tools like crab for running many fits with high parallelism. For this to work, the way that tasks handle their inputs and outputs has to be compliant with law remote targets. However, as it turns out, this is already mostly the case and there are just a few changes + 2 minor fixes required:
--workers >1) → Most likely another weird interference with PyROOT.Closes #25 (closed).