BUG_FIX: smooth_lowess was broken due to wrong import.
Automatic style corrections courtesy of autopep8.
lowess: add meaningful ValueError exceptions.
Automatic style corrections courtesy of autopep8.
Merge remote-tracking branch 'tomas/BUGFIX_repr_utf8' into 0.7.2
Improve SmoothingLowess UI by using Range instead of Int
Remove broken numerical differention from smooth_lowess and smooth_tv.
Replace in-house savitzky-golay with scipy one.
Replace in-house lowess smoothing with statsmodels one.
Add +/- buttoms to savitzky-golay UI.

Also decrease code duplication and remove differential order from
`smooth_lowess`.
smooth_lowess uses Signal.map.
split processing from UI in smooth_tv and smooth_savitzky_golay
Merge branch 'ropeproject_gitignore' into BUG_FIX_smooth_lowess
Merge remote-tracking branch 'magnus/fix_element_Mo_eels_edge' into 0.7.2
Merge branch '0.7.2' into BUG_FIX_smooth_lowess
Add smoothing tests
Fix estimate_elastic_scattering_threshold that was broken due to savgol arg name change.
Merge branch 'Disable_progressbar' into BUG_FIX_smooth_lowess
Add show_progressbar argument to smooth_tv and smooth_lowess
Improve smooth methods docstring