Fixes #287
Merge pull request #309 from francisco-dlp/BUG_FIX_second_pointer

Bug fix second pointer
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
BUG: EDS TEM missing_parameters()
Merge pull request #320 from pburdet/BUG_eds_tem_missing_parameters

BUG: EDS TEM missing_parameters()
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.
New EELSModel._get_first_ionization_edge_energy method.