* Add prune feature to cli to remove duplicated entries as a workaround to https://github.com/decompals/frogress/issues/27
usage: cli.py prune [-h] project version
positional arguments:
project the project for which to prune the entries
version the slug for the version
optional arguments:
-h, --help show this help message and exit
* Reformat cli.py with Black
* Improve help info for new added prune option
It is used to fix duplicates caused by https://github.com/decompals/frogress/issues/27