use latest yarn when running CI

oliverlaz · oliverlaz · commit dde3f4a19882 · 2019-02-15T15:37:54.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -3,5 +3,8 @@ language: node_js
 node_js:
   node
 
+before_install:
+  - curl -o- -L https://yarnpkg.com/install.sh | bash
+
 cache:
   yarn: true
