fix scalacOptions (#651)
fix scalacOptions (#651)

- "-Xfuture" is deprecated since Scala 2.13 https://github.com/scala/scala/commit/67195a5cffadac9340b3228ee804e01a0fc02e25
- "-Ywarn-unused-import" is replaced by "-Ywarn-unused:imports" since Scala 2.12
julien-truffaut/Monocle