* New features
* Added some convenience features to `tomotopy.LDAModel.train` and `tomotopy.LDAModel.set_word_prior`.
* `LDAModel.train` now has new arguments `callback`, `callback_interval` and `show_progres` to monitor the training progress.
* `LDAModel.set_word_prior` now can accept `Dict[int, float]` type as its argument `prior`.