build: Downgrade to Java 1.7

Downgrading is necessary to keep compatibility with Android

Change-Id: I9269d3ec32fd87bdd487ec91fab0f6fa87c7de23
diff --git a/.travis.yml b/.travis.yml
index 9bcf999..e358d25 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,3 +1,3 @@
 language: java
 jdk:
-  - oraclejdk8
+  - oraclejdk7