Data-utilities

* **Added `sklearn_utilities`**.
* Improved tests customization in `du.test`.
* Greatly improved documentation to `matplotlib_utilities`.
* Greatly expanded `pandas_utilities` functions.
* Improved tests as a whole.

* Greatly improved `matplotlib_utilities` module.

* Removed dependency with `unidecode` module.

* tests: enabled parametrized tests invocations such as:
`python3 -c "import data_utilities as du; du.test(label='fast')"`
`python3 -c "import data_utilities as du; du.test(N=500)"`

* Add a test for the `test_support` file itself.

* Other
* Stable version uploaded to pypi

* Other
* Development versions uploaded to pypi

<!---
* `matplolib_utilities`
* A

* `pandas_utilities`
* A

* `python_utilities`
* A
-->

* Other
* Added package to PyPA as `data_utilities`
* Added a test method to the package:
python3 -c `import data_utilities as du; du.test()`

* Improved `histogram_of_dataframe` function: added a textbox with summary
statistics.

* Added a function to scale axes axis (`scale_axes_axis`).

* Added a colorbar argument to `plot_3d`.

* Label containers now return a list of matplotlib Text objects.

* Added a boolean column to `dummy_dataframe`.

* Added a test module for other libraries: `matplotlib_utilities` and
`python_utilities`.

* Cleaned up the code.