python/scripts/aubiocut: use stamp, not onset
python/scripts/aubiocut: add -o, --output directory option
python/lib/aubio/slicing.py: rewrite slicing loop from aubiocut, add some tests
python/scripts/aubiocut: use slice_source_at_stamps
python/lib/aubio/__init__.py: import slicing
python/lib/aubio/slicing.py: error checking, add more tests, use get_default_sound
python/lib/aubio/slicing.py: improve slicing, make tests faster
python/tests/sounds: deleted
python/lib/aubio/slicing.py: next_stamp can be 0
python/lib/aubio/slicing.py: use start and end stamps, make sure read > 0, improve tests
lib/aubio/slicing.py: allow any regions, overlaping or not, add more tests
python/lib/aubio/slicing.py: fix zero padding in slice names
python/lib/aubio/slicing.py: also add end if adding start at 0
python/scripts/aubiocut: add --cut-until-nsamples and --cut-until-nslices options