Merge pull request #194 from dwijnand/2123

Finish upgrading to Scala 2.12.3

Author: dwijnand

project/Build.scala

@@ -29,7 +29,7 @@ object BuildSettings {
       scalaVersion := sys.props.getOrElse("mima.buildScalaVersion",
         (CrossVersion partialVersion (sbtVersion in pluginCrossBuild).value match {
           case Some((0, 13)) => "2.10.6"
-          case Some((1, _))  => "2.12.2"
+          case Some((1, _))  => "2.12.3"
           case _             => sys error s"Unhandled sbt version ${(sbtVersion in pluginCrossBuild).value}"
         })
       ),