fix(travis): fix script commands

Author: pine

.travis.yml

@@ -5,10 +5,14 @@ node_js:
   - 8
   - stable
 
-scripts:
+before_install:
+  - curl -o- -L https://yarnpkg.com/install.sh | bash -s -- --version 1.3.2
+  - export PATH=$HOME/.yarn/bin:$PATH
+script:
   - travis_retry yarn test
 
-cache: yarn
+cache:
+    yarn: true
 
 env:
   global: