ci(travis): use build config validation (beta) [skip ci]

myii · myii · commit d2f7fe24a190 · 2019-11-13T16:49:07.000Z
* Automated using myii/ssf-formula#97
diff --git a/.travis.yml b/.travis.yml
@@ -3,6 +3,7 @@
 ---
 ## Machine config
 dist: bionic
+version: '~> 1.0'
 sudo: required
 services:
   - docker
