Checkdigit

🐛 Bugfixes
------------

- Fixed a bug where ISBN-13 calculations allowed for a check digit of X, which shouldn't be possible. Thanks to mohsenBanan for the bug report 171.



[Full Changelog](https://checkdigit.readthedocs.io/en/latest/changelog.html)

**Commits**: https://github.com/harens/checkdigit/compare/v0.4.0...v0.5.0

Please see the [changelog](https://checkdigit.readthedocs.io/en/latest/changelog.html#changelog).

Please see the [changelog](https://checkdigit.readthedocs.io/en/latest/changelog.html#changelog).

__Compatability Broken__: A single ISBN function is now available, rather than the two separate ones for ISBN-10 and ISBN-13. (19 63)

For the full changelog, please see [here](https://checkdigit.readthedocs.io/en/latest/changelog.html#changelog).

__Breaking change__: Parity methods no longer return the full block of data, so as to match the other check digit methods. They instead return the missing bit.

Formats

- CRC Format Added (Thanks sapieninja!)
- Refactored ISBN and Luhn code

Docs
- Revamped the README
- Move docs to RTD

Behind the scenes
- Transition tests from error404 to pytest
- Add the all-contributors bot, to celebrate everyone's contributions!

Adds GS1 capability, kindly submitted by OtherBarry https://github.com/harens/checkdigit/pull/38. 🎉