Update Scala and dependencies versions

Author: romac

build.sbt

@@ -3,18 +3,25 @@ import ScalaZ3Build._
 lazy val root = (project in file("."))
   .settings(
     name := "ScalaZ3",
-    version := "3.0",
+    version := "4.0",
     organization := "ch.epfl.lara",
     scalacOptions ++= Seq(
       "-deprecation",
       "-unchecked",
       "-feature",
     ),
-    scalaVersion := "2.12.7",
-    crossScalaVersions := Seq("2.10.7", "2.11.12", "2.12.7"),
+    scalaVersion := "2.12.8",
+    crossScalaVersions := Seq("2.10.7", "2.11.12", "2.12.8"),
     libraryDependencies ++= Seq(
-      "org.scalatest" %% "scalatest" % "3.0.1" % "test"
+      "org.scalatest" %% "scalatest" % "3.0.7" % "test"
     ),
+    libraryDependencies ++= {
+      CrossVersion.partialVersion(scalaVersion.value) match {
+        // if scala 2.11+ is used, add dependency on scala-xml module
+        case Some((2, scalaMajor)) if scalaMajor >= 11 => Seq("org.scala-lang.modules" %% "scala-xml" % "1.2.0")
+        case _                                         => Seq.empty
+      }
+    },
     fork in Test := true,
     checksumKey := checksumTask.value,
     gccKey := gccTask.value,

project/build.sbt

@@ -4,3 +4,4 @@ libraryDependencies ++= Seq(
   "org.slf4j" % "slf4j-log4j12" % "1.7.25"
 )
 
+scalacOptions ++= Seq("-deprecation", "-feature")