Rdap-cli

Added
- New internal function to make more generic the alert messages.

Changed
- Changed output messages in some commands.

Fixed
- Fixed an unexpected exception when passing an invalid file format.
- Typos.

Added
- Short tutorial in the user_guide.md
- History download command example in history.md

Fixed
- typos in gather.md

Changed
- Moved the Save class into a common dir to be used by multiple operations.
- Changed the gather option --save into --file.
- Internal function to convert dict into text before saving now support lists.
- Badges in README.md

Added
- Added a new subcommand to history 'download'.

Deleted
- Deleted some unused exceptions.
- Deleted unused files in gather command directory.

Changed
- Documentation switched to absolute links.

Added
- Added a file reader in setup.py to show the README.md in the Pypi.

Fixed
- Bugfix on command version.

Changed
- Changed the default length of uuid displayed in the history table to 8

Fixed
- Bugfix. History and dns files now downloads in root.