Fixes #288 by making the noise addition optional.

Also, now it uses the noise properties from metadata if present.
Automatic style corrections courtesy of autopep8.
Merge pull request #290 from francisco-dlp/BUG_FIX_spikes_removal_tool_noise

Bug fix spikes removal tool noise
calculates chisq only for active components
added tests for inactive component bug
Automatic style corrections courtesy of autopep8
Merge branch 'chi_squared' into ENH_component_active_pixel
Reimplemented, now 'enable_pixel_level_switching' is False by default, so active_map is not used by default, fixed tests to reflect it
Automatic style corrections courtesy of autopep8
Merge branch 'ENH_component_active_pixel' into model_as_dict

Conflicts:
	hyperspy/model.py