Upgrade the version of Scala to 2.12

[sj123050037]

No description provided.

[raboof]

sbt-revolver is cross-built for sbt 0.13.18 and sbt 1.2.8.

When building for sbt 0.13 we must use Scala 2.10, when building for sbt 1.2 we must use Scala 2.12.

You can build for sbt 1.2 with ^^1.2.8 as documented in https://www.scala-sbt.org/1.x/docs/Cross-Build-Plugins.html .

So I think this is already OK, but perhaps we should switch to make the sbt 1.2 build the default.

[sj123050037]

Thanks, it helps!