Fixes #175 , plotting line spectra was raising an exception.
Merge branch 'master' into BUG_FIX_plot_line_spectra

Conflicts:
	hyperspy/signal.py
Automatic style corrections courtesy of autopep8.
Merge pull request #178 from francisco-dlp/BUG_FIX_plot_line_spectra

Fixes #175 , plotting line spectra was raising an exception.