Pxtextmining

Two major changes:
1. `setup.py` has been enriched with additional information. Dependencies have also been added;
2. The Readme explains in detail how to install the package from PyPI or GitHub;

Added KBins Discretizer. Release 0.2.4 was supposed to do that, but I made a mistake in the process and never merged into main. Much easier to create another release (0.2.5) than go back and revert everything. After all, this is a pre-release, so I am not that worried about the looks of the repo's history.

Pre-release [0.2.0](https://github.com/CDU-data-science-team/pxtextmining/releases/tag/0.2.0) with all the most up-to-date hotfixes.