v0.4.1

Fixed

• Log.modalities, Log.locations, and Log.modality_sensors no
  longer crash on Log objects loaded from very-old pickles where
  per-:class:Signal meta is empty. All three now derive from
  :attr:Log.sensors — repaired by :meth:Sensor.__setstate__ — so
  they resolve on the same pickles that the 0.4.0
  clean_emg_ekg_artifact() fix already handled. As a side effect
  Log.locations (previously raising AttributeError because
  Signal has no .location property — broken on every load,
  not just stale pickles) now returns the set of
  sensor.location values, and Log.modality_sensors returns
  {modality: {sensor.name, ...}} instead of the documentation-
  contradicting {modality: {modality_as_attr_name}} it produced
  before. No internal callers depended on the old behavior.