SAMOA-4: Specify target JDK for Travis CI build
Fixes #5
diff --git a/.travis.yml b/.travis.yml
index 5e4bbb6..abf6e2f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,8 @@
 language: java
 
+jdk:
+- oraclejdk7
+
 install:
 - git clone https://github.com/apache/incubator-s4.git
 - cd incubator-s4