Running experiments with more that 1 worker

[kimberley-faria]

Replicate issue: Running the Seldonian experiment section of the fair loans tutorial (or any tutorial) on Windows:

When running the generate_threeplots.py script, getting error:

Traceback (most recent call last):
  File "C:\Users\faria\PycharmProjects\seldonian_project\fair_loans\run_experiments.py", line 87, in <module>
    plot_generator.run_baseline_experiment(
  File "C:\Users\faria\anaconda3\envs\seldons_playground\lib\site-packages\experiments\generate_plots.py", line 572, in run_baseline_experiment
    bl_exp.run_experiment(**run_baseline_kwargs)
  File "C:\Users\faria\anaconda3\envs\seldons_playground\lib\site-packages\experiments\experiments.py", line 152, in run_experiment
    mp_context=mp.get_context('fork')) as ex:
  File "C:\Users\faria\anaconda3\envs\seldons_playground\lib\multiprocessing\context.py", line 239, in get_context
    return super().get_context(method)
  File "C:\Users\faria\anaconda3\envs\seldons_playground\lib\multiprocessing\context.py", line 193, in get_context
    raise ValueError('cannot find context for %r' % method) from None
ValueError: cannot find context for 'fork'