Fixes #287
Merge branch 'BUG_FIX_estimate_elastic_scattering_threshold' into 0.7.1
Merge branch 'BUG_FIX_fourier_ratio_single_spectrum' into 0.7.1
Merge branch 'ENH_spikes_removal_tool_update' into 0.7.1
Merge branch 'BUG_FIX_second_pointer' into 0.7.1
ENH: Beam energy units

Make sure the beam
energy has the right units
Automatic style corrections courtesy of autopep8
BUG: stack(axis='x') not working
Test
EHN: Xray energy from Chantler2005
EHN: factor to weight
Automatic style corrections courtesy of autopep8
bugfix: fit_background was wrongfully erasing the first active edge
EHN: _get_energy_xray_line
Automatic style corrections courtesy of autopep8
EHN: eds._get_line_energy
Merge branch 'ENH_beam_energy_units' into EHN_tidy_energy
Merge pull request #316 from AEljarrat/bugfix_smart_fit

bugfix: fit_background was wrongfully erasing the first active edge
BUG_FIX: two_area_background_estimation was raising an exception when not PowerLaw component in model.
Automatic style corrections courtesy of autopep8.