Use `dist: trusty` for Travis CI
diff --git a/.travis.yml b/.travis.yml
index 412a660..ce0f7e0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -14,6 +14,7 @@
 # limitations under the License.
 
 language: java
+dist: trusty
 sudo: false
 
 jdk: