* Change `convertor` to `converter` in all model APIs
* Improve `ReduceLRUponNan` callback function
* WardLT major contributions to the `MolecularGraph` class
* Add serialization methods for `local_env` classes
* delete `data/mp.py`
* GraphModel and MEGNetModel now supports a metadata tag, which is included in
the JSON. (suggestion of mhorton).
* Misc bug fixes for edge cases as well as improved error messages for
mismatches in inputs.
* Implement the option for a scaler in models, which is used in efermi models at
the moment but also can be helpful for extensive quantities.
* Minor fixes to setup.py and licenses.
* Proper fix to release on PyPi.
* Major refactoring to conform to OOP principles. Note that the
changes are not backwards compatible, but many things are a lot
simpler. We do not expect much disruption to existing users.
* Added pre-trained models developed in our work for users who
wish to simply use them for prediction.
* Major improvements to README and documentation.
* Bug fix for dimension problem when only one atom in structure