Add select --latest and select --latest-prerelease

[JacobHearst]

Closes #160

Some notes:

• Linting is mentioned in CONTRIBUTING.md but I didn't see any linting configurations in the project nor any mention of a specific linting tool
• XcodeInstaller.InstallationType felt like overkill for this use case so I stuck with simple bool flags but I'm also happy to refactor this to use it.