ICB-DCM/pyPESTO: pyPESTO 0.2.6

Objective: Basic finite differences (#666) Fix factor 2 in res/fval values (#619) Optimization: Sort optimization results when appending (#668) Read optimizer result from HDF5 (previously only CSV) (#663) Storage: Load ensemble from HDF5 (#640) CI: Add flake8 checks as pre-commit hook (#662) Add efficient biological conversion reaction test model (#619) General: No automatic import of the predict module (#657) Assert unique problem parameter names (#665) Load ensemble from optimization result with and without history usage (#640) Calculate validation profile significance (#658) Set pypesto screen logger to "INFO" by default (#667) Minor fixes: Fix axis variable overwriting in visualize.sampling_parameter_traces (#665