request: Declare version scheme / policy

[ches]

It is common for real-world applications to have several versions of scala-logging in their dependency graphs, which leads to sbt giving eviction warnings.

I couldn't find a documented versioning policy, so I'm not sure when I should be worried. sbt now offers a more formal way than documentation, in the versionScheme setting that libraries can declare. It'd be great if scala-logging's build/artifacts include this.

Perhaps sbt-version-policy, or MiMa alone, can be employed to keep us honest.

[SethTisue]

I believe a pull request in this area would be highly welcome.

[analytically]

Any opinion on what setting we should use?