Add support for checkstyle xml format

[ccommissoTrust]

Tailor Version: v0.12.0

Swift Version: Apple Swift version 4.0.2 (swiftlang-900.0.69.2 clang-900.0.38)

Platform (Mac/Linux/Windows/CI): Mac

Installation Method: Homebrew

It would be nice to be able to feed in the results of tailor into Jenkins CI. Would it be possible to add a new formatter that produces checkstyle xml output so we can feed in the report to the Jenkins Checkstyle plugin?

I searched for json to checkstyle converters (along with PMD and Findbugs) but no luck at finding anything useful.