Rdt

In this release we drop the support for the now officially dead Python 3.5
and introduce a new feature in the DatetimeTransformer which reduces the dimensionality
of the generated numerical values while also ensuring that the reverted datetimes
maintain the same level as time unit precision as the original ones.

* Drop Py35 support - Issue [129](https://github.com/sdv-dev/RDT/issues/129) by csala
* Add option to drop constant parts of the datetimes - Issue [130](https://github.com/sdv-dev/RDT/issues/130) by csala

* Add GaussianCopulaTransformer - Issue [125](https://github.com/sdv-dev/RDT/issues/125) by csala
* dtype category error - Issue [124](https://github.com/sdv-dev/RDT/issues/124) by csala

Miunor bugfixing release.

Bugs Fixed

* Handle NaNs in OneHotEncodingTransformer - Issue [118](https://github.com/sdv-dev/RDT/issues/118) by csala
* OneHotEncodingTransformer fails if there is only one category - Issue [119](https://github.com/sdv-dev/RDT/issues/119) by csala
* All NaN column produces NaN values enhancement - Issue [121](https://github.com/sdv-dev/RDT/issues/121) by csala
* Make the CategoricalTransformer learn the column dtype and restore it back - Issue [122](https://github.com/sdv-dev/RDT/issues/122) by csala

General Improvements

* Support Python 3.8 - Issue [117](https://github.com/sdv-dev/RDT/issues/117) by csala
* Support pandas >1 - Issue [116](https://github.com/sdv-dev/RDT/issues/116) by csala

* Implement OneHot and Label encoding as transformers - Issue [112](https://github.com/sdv-dev/RDT/issues/112) by csala

Bugs Fixed

* Escape `column_name` in hypertransformer - Issue [110](https://github.com/sdv-dev/RDT/issues/110) by csala