Update to scala 2.12.1 refs #235 . Add Forth.scala - refs #137 (#251)

Author: ricemery

exercises/forth/build.sbt

@@ -1,5 +1,5 @@
-scalaVersion := "2.11.7"
+scalaVersion := "2.12.1"
 
 
-libraryDependencies += "org.scalatest" % "scalatest_2.11" % "2.2.5" % "test"
+libraryDependencies += "org.scalatest" %% "scalatest" % "3.0.1" % "test"
 libraryDependencies += "org.scala-lang.modules" %% "scala-parser-combinators" % "1.0.4"

exercises/forth/src/main/scala/Forth.scala

@@ -0,0 +1,6 @@
+import ForthError.ForthError
+
+
+class Forth extends ForthEvaluator {
+  def eval(text: String): Either[ForthError, ForthEvaluatorState] = ???
+}