Update scala to 2.12.7

Author: stringbean

.travis.yml

@@ -3,7 +3,7 @@ sudo: false
 
 scala:
   - 2.11.11
-  - 2.12.3
+  - 2.12.7
 jdk:
   - oraclejdk8
 

build.sbt

@@ -4,7 +4,7 @@ import com.typesafe.sbt.SbtGit.GitKeys._
 organization := "software.purpledragon.xml"
 version := "0.0.3-SNAPSHOT"
 
-scalaVersion := "2.12.6"
+scalaVersion := "2.12.7"
 crossScalaVersions := Seq(scalaVersion.value, "2.11.12")
 
 // dependencies common for all sub-projects