ci: Use yarn as default dependency management system

a60814billy · a60814billy · commit cdd8a72d04d6 · 2017-03-24T07:22:02.000+08:00
Use yarn in TravisCI
diff --git a/.travis.yml b/.travis.yml
@@ -11,3 +11,4 @@ addons:
       - ubuntu-toolchain-r-test
     packages:
       - g++-4.8
+cache: yarn
