Pganonymize

* [15 Fix for exclude bug](https://github.com/rheinwerk-verlag/pganonymize/pull/15) ([abhinavvaidya90](https://github.com/abhinavvaidya90))

* [13 Fixed a syntax error if no truncated tables are defined](https://github.com/rheinwerk-verlag/pganonymize/pull/13) ([ray-man](https://github.com/ray-man))

* Use [`python-poetry`](https://github.com/python-poetry/poetry) for requirements management
* Added commandline argument to list all available providers (4)
* Added commandline argument to create a dump file (5)
* Execute table truncation in one statement to avoid foreign key constraint errors (thanks to [W1ldPo1nter](https://github.com/W1ldPo1nter))

* Fixed several issues with the usage of ``dict.keys`` and Python 3

* Fixed the wrong cStringIO import for Python 3
* Removed Travis-CI file in favor of the Github actions

* Hide the progressbar completely if verbose is set to ``False``
* Restructured the requirement files and added flake8 to Travis CI