Audinterface

--------------------------

* Changed: ``Feature.process_func()`` supports more shapes, namely
``(features)``
``(channels, features)``
``(features, frames)``
``(channels, features, frames)``
* Changed: ``Feature.process_func()`` supports more types
(e.g. scalars, lists, strings, etc.)
* Fixed: ``Feature.__call__()`` always returns ``(channels, features, frames)``

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* Fixed: CHANGELOG

--------------------------

* Added: ``utils.signal_index()`` to create a segmented index without file level
* Changed: use keyword argument with ``pandas.MultiIndex.set_levels()``
* Fixed: raise error if multiple frames are returned but ``win_dur`` is not set
* Fixed: remove ``num_channels`` from ``Feature`` docstring

--------------------------

* Added: tests on Windows and macOC

--------------------------

* Added: ``root`` argument to all functions processing file input

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* Fixed: avoid using 'sec' as unit in ``pd.to_timedelta()`` for backward compatibility