style: convert tabs to 4 spaces
fix: Segment.__closest_frame was shifted by 0.5*step seconds
feat: new YaafeFrame sliding window
style(test): convert tabs to 4-spaces
chore: replace deprecated Annotation.iterlabels() by Annotation.itertracks(label=True)
chore(test): replace deprecated LabelMatrix.iter_values() by LabelMatrix.itervalues()