[build] format travis.yml

.travis.yml

@@ -1,22 +1,22 @@
 language: node_js
 sudo: required
 addons:
-    chrome: stable
+  chrome: stable
 node_js:
-- 10
+  - 10
 os: linux
 cache:
   yarn: true
 branches:
   only:
-  - master
-  - dev
+    - master
+    - dev
 install:
-- |
+  - |
     yarn install
 script:
-- |
+  - |
     npm run lint && npm run test
 after_success:
-- |
+  - |
     cat ./test/coverage/lcov.info | ./node_modules/.bin/codecov