.travis.yml: add openjdk6

PascalSchumacher · PascalSchumacher · commit ccc2b43def74 · 2017-07-28T17:30:58.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -17,6 +17,7 @@ language: java
 sudo: false
 
 jdk:
+  - openjdk6
   - openjdk7
   - oraclejdk8
 
