Release v0.9.0

• Added: auinterface.utils.sliding_window()
• Added: auinterface.utils.to_timedelta()
• Added: argument
  process_func_applies_sliding_window
  to
  audinterface.Feature
• Added: arguments
  win_dur and hop_dur
  to
  audinterface.Process
• Added: arguments
  min_signal_dur and max_signal_dur
  to
  audinterface.Feature,
  audinterface.Process,
  audinterface.Segment
• Added: argument
  cache_root
  to
  audinterface.Feature.process_index(),
  audinterface.Process.process_index()
• Changed: extend documentation with docstring examples and usage section
• Deprecated: unit argument of audinterface.Feature,
  instead specify unit directly when providing duration arguments,
  compare audinterface.utils.to_timedelta()
• Fixed: audinterface.ProcessWithContext
  requires one output for every segment