Switch to Scala 2.12.7 (#42)

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index 5f63c29..be01063 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,7 +5,7 @@
 group: deprecated-2017Q3
 language: scala
 scala:
-- 2.11.11
+- 2.12.7
 services:
   - docker
 before_install:

settings.gradle

diff --git a/settings.gradle b/settings.gradle
index c7e3ab7..f9a1986 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -27,7 +27,7 @@
 ]
 
 gradle.ext.scala = [
-    version: '2.11.11',
+    version: '2.12.7',
     compileFlags: ['-feature', '-unchecked', '-deprecation', '-Xfatal-warnings', '-Ywarn-unused-import']
 ]