Use semantic versioning

For the new release, I suggest to switch from version 1 to semantic versioning (https://semver.org/). Depending on how far the package evolved since 2014, the next version could be 2.0.0 or 1.1.0

https://github.com/gap-packages/rig/blob/31e826a68540ce7827189c57e79b1fbc820a14d5/PackageInfo.g#L4