upgrade CI

Update build.sbt

Update build.sbt

prep 3.1.0

Update VERSION3.md

Update VERSION.md

try to fix compile issues (#801)

Update EnumerationSerializerModule.scala

Update EnumerationSerializerModule.scala (#799)

Update sbt version to 1.12.1

avoid casting

Update VERSION3.md

back to 3.1.0-SNAPSHOT

prep 3.1.0-rc1

Change jacksonVersion and modify resolver configuration