Some pep8 changes

nifty4/library/critical_power_curvature.py

nifty4/library/critical_power_energy.py

nifty4/library/log_normal_wiener_filter_energy.py

nifty4/library/noise_energy.py

nifty4/library/nonlinear_power_curvature.py

nifty4/library/nonlinear_power_energy.py

nifty4/library/nonlinear_wiener_filter_energy.py

nifty4/library/response_operators.py

nifty4/library/wiener_filter_energy.py

test/test_energies/test_map.py

test/test_energies/test_noise.py

test/test_energies/test_power.py