---------------------
- Migrated serialization setup to ``jsonpickle``, a practice much saner than
what I had been previously doing. This breaks backward compatibility with
v0.1.4 JSON blobs, but enables far more flexibility in what can be serialized
- replace older ``(de)serialize()`` methods with much saner ``get_header()``
and ``get_row()`` for export of models as ``DataFrame`` rows (e.g. to watch
parameter trajectories during training
- ``train_baum_welch()`` can now weight individual observations
- changed logging in ``train_baum_welch()``. This led to some
backward-incompatible changes, but is much nicer. It also includes a
``DefaultLoggerFactory()`` so people don't have to comb through insane
logs anymore
- Unit tests and multiple improvments for ``train_baum_welch()``