Ginpar

Use the API from the docs for sketch data files.

This is a hotfix for 25

Major changes

- Commands
- Implement `ginpar new [SKETCH]`
- Create a new sketch inside the project's `config.content_path`
- Use boilerplate code for sketches that already includes variables for dimensions.
- Implement `ginpar serve`
- Starts a new live-reloading server.
- Builds on every file change inside `config.content_path`.
- Update `ginpar quickstart`
- Instead of copying files from the pypi package into the working directory, it clones a GitHub repository with the contents of the quickstart project, and removes all `.git*` files.
- API
- Use YAML instead of JSON for the site config file
- Easier to read and write.
- YAML is a superset of JSON, so users are still able to write in JSON.

Minor changes

- Tests
- Implement tests for all the CLI commands except `serve`.
- Docs
- Adopt numpydocs as the docstring style

Major changes
- Create a working CLI using `click`.
- `build`, `quickstart`, and `init` are now commands callable like `ginpar [COMMAND]`.
- `quickstart` and `init` can be forced with `-f` to remove any interfering file or directory.
- `quickstart`, `init`, and `build` can take a custom path to create/parse the sketches, and to publish the generated page.

Minor changes
- Move all the utilities from `utils.py` to `utils/` and group them by functionality:
- `echo.py`: Echoing functions for te CLI.
- `files.py`: File and directory management: delete, create, or copy.
- `strings.py`: String formatting and filtering to work with kebab, snake, and spaced.