Travis makes us work harder now to actually get OpenJDK 6

as per:
travis-ci/travis-ci#8199 (comment)

Author: SethTisue

.travis.yml

@@ -10,10 +10,13 @@ env:
     - secure: "Cj4PsumsWL37Pl7V5ZPJw+/xH9esHblG5nN9Op91XcCfG006xHsz2w1iNOqFqCF8wAhgObuA2CmAH3ZuI1jZGGSo2HMt9+f5Z6tpifFzsTHZJtdNIVOpS3/NGhvgtg3UnT5WQQtnVi6zlkKl1xCpAIDNhOJ9dXoL54auAqvxpko="
 script:
   - admin/build.sh
+addons:
+  apt:
+    packages:
+      - openjdk-6-jdk
 jdk:
   - openjdk6
   - oraclejdk8
 notifications:
   email:
-    - jason.zaugg@typesafe.com
-    - philipp.haller@typesafe.com
+    - jason.zaugg@lightbend.com