upgrade travis build distribution image to xenial

mohsinulhaq · mohsinulhaq · commit 7c167b92dd5c · 2018-12-09T15:55:19.000+05:30
diff --git a/.travis.yml b/.travis.yml
@@ -1,7 +1,11 @@
 language: node_js
+dist: xenial
 node_js:
   - 'stable'
 cache: yarn
+branches:
+  only:
+    - master
 script:
   - yarn lint
   - yarn test
