Ktrain

New:
- `Transformer` API in *ktrain* now supports using community-uploaded transformer models
- added `shallownlp` module with out-of-the-box NER for English, Russian, and Chinese
- `text.eda` module now supports NMF in addition to LDA

Changed:
- `texts_from_csv` and `texts_from_df` now accept a single column of labels in string format and will
1-hot-encode labels automatically for classification or multi-class classification problems.
- reorganized language-handling to `text.textutils`
- more suppression of warnings due to spurious warnings from TF2 causing confusion in output
- `classes` argument to `Transformer` constructor has been changed to `class_names` for consistency with `texts_from_array`

Fixed:
- N/A

New:
- N/A

Changed:
- changed pandas dependency to `>=1.0.1` due to bug in pandas 1.0

Fixed:
- N/A

New:
- N/A

Changed:
- Transformed data containers for transformers, NER, and graph -node classification to be
instances of `ktrain.data.Dataset`.

Fixed:
- fixed `images_from_array` so that y labels are correctly 1-hot-encoded when necessary
- correct tokenization for `bert-base-japanese` Transformer models from PR 57

New:
- N/A

Changed:
- Removed Exception when `distilbert` is selected in `text_classifier` for non-English language after
[Hugging Face fixed the reported bug](https://github.com/huggingface/transformers/issues/2462).

Fixed:
- XLNet models like `xlnet-base-cased` now works after casting input arrays to `int32`
- modified `TextPredictor.explain` to propogate correct error message from `eli5` for multilabel text classification.

New:
- N/A

Changed:
- N/A

Fixed:
- fixed `utils.nclasses_from_data` for `ktrain.Dataset` instances
- prevent `detect_lang` failing when Pandas Series is supplied

New:
- support for out-of-the-box text regression in both the `Transformer` API and conventional API (i.e., `text.text_regression_model`).

Changed:
- `text.TextPreprocessor` prints sequence length statistics

Fixed:
- auto-detect language when using `Transformer` class to prevent printing `en` as default