Exclude yanked releases when choosing baseline version

[mgr0dzicki]

Closes #254

Extracts the selection of baseline version to a separate function, adds tests for it.

[obi1kenobi]

I'm excited to have test coverage on this tricky logic! Thanks for putting it together.

It would be good to add two more test cases that check & document that when all versions are either yanked or pre-releases, cargo-semver-checks will pick the largest-numbered version regardless of whether it's been yanked or is a pre-release. (One test where it's yanked and one where it's a pre-release.)

[mgr0dzicki]

It would be good to add two more test cases that check & document that when all versions are either yanked or pre-releases, cargo-semver-checks will pick the largest-numbered version regardless of whether it's been yanked or is a pre-release. (One test where it's yanked and one where it's a pre-release.)

Added! They revealed that my logic of handling yanked versions was not behaving as it should (it was ignoring yanked releases when there weren't any normal one). I fixed this.

[obi1kenobi]

This looks good to me! @tonowak if your concerns are also resolved, let's merge?