Merge pull request #274 from Dwolla/update/scala-library-2.12.20

Update scala-library to 2.12.20

build.sbt

@@ -1,5 +1,5 @@
 lazy val V = new {
-  val SCALA_2_12 = "2.12.19"
+  val SCALA_2_12 = "2.12.20"
   val SCALA_2_13 = "2.13.14"
   val Scalas = Seq(SCALA_2_13, SCALA_2_12)
 }