🐛 fix travis build

Author: Wei Li

.travis.yml

@@ -1,5 +1,8 @@
 ---
 sudo: required
+# Various issues have been logged aginst Travis-ci about Java 7 Support. Looks like it's broken on the latest Linux image.
+# For now we use the old version of the image. In the longer term, we should consider moving to Java 8
+group: deprecated-2017Q2
 
 services: 
   - docker