Add yarn cache support for travis.

cyrilschumacher · cyrilschumacher · commit 0f27b90f099e · 2017-09-28T16:24:52.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -5,6 +5,10 @@ node_js:
   - "7"
   - "6"
   - "5"
+cache:
+  yarn: true
+  directories:
+    - node_modules
 install:
   - yarn
 script:
