Muttlib

Closes 92 - pylint `file_processing.py`

Closes 101 - Add tests to `ipynb_utils.py`:

- Add tests to `ipynb_utils` module.
- Remove plotting methods:
- `top_categorical_vs_kdeplot`
- `top_categorical_vs_heatmap`
- `plot_agg_bar_charts`
- `plot_category2category_pie_charts`
- `plot_timeseries`

Closes 106 - Add --verbose option to twine upload

Refactor to dbconn imports simpler.

Refactor dbconn param parsing to use SQLAlchemy `make_url`.

Added

- This CHANGELOG file.

Changed

- Use psycopg2-binary for postgres db connection.
- Give warnings about missing mysql and postgres modules.