install latest yarn on travis before proceeding

mohsinulhaq · mohsinulhaq · commit 72e44b4d2c48 · 2019-01-14T00:32:39.000+05:30
diff --git a/.travis.yml b/.travis.yml
@@ -2,6 +2,9 @@ dist: xenial
 language: node_js
 node_js:
   - '--lts'
+before_install:
+  - curl -o- -L https://yarnpkg.com/install.sh | bash
+  - source ~/.bashrc
 cache: yarn
 branches:
   except:
