Change multiprocessing backend

[cbouy]

Switch from multiprocessing to another concurrency library that doesn't use pickle to copy objects for each process in the pool.

Requirements:

• The package must use a better pickling library, such as dill
• Support for custom interactions defined in notebooks (see Issue Error when overwriting new interactions #86)

Tracklist:

• Investigate: multiprocess uses dill which should be suitable, joblib?
• Implement
• Test in different environments: script, notebook