Monix: Version 2.0.6 Maintenance Release

This release is binary compatible with 2.0.x, being a maintenance. In order to upgrade, just increment the version number in build.sbt:

libraryDependencies += "io.monix" %% "monix" % "2.0.6"

This version is published for Scala 2.12.0 final release, incrementing the dependency on Minitest to 0.27 and on Scalaz to 7.2.7.