Idutils

- Changes ISBN normalization to use `isbnid` instead of `isbnlib`. Now,
importing this library will not change the default socket timeout, resulting
in unwanted side effects.

- Changes URL resolution for DOIs to use https://doi.org instead of
http://dx.doi.org according to
https://www.doi.org/doi_handbook/3_Resolution.html#3.8

- Fixes GND validation and normalization.
- Replaces invalid package name in `run-tests.sh` and makes `run-tests.sh` file
executable. One can now use `docker-compose run --rm web /code/run-tests.sh`
to run all the CI tests (pep257, sphinx, test suite).
- Initial release of Docker configuration suitable for local developments.
`docker-compose build` rebuilds the image,
`docker-compose run --rm web /code/run-tests.sh` runs the test suite.

- First public release.