chore: change run order

Christoph Bühler · Christoph Bühler · commit 02002743b13c · 2017-07-04T16:45:09.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -9,9 +9,9 @@ notifications:
   email: false
 
 node_js:
-  - '6'
-  - '7'
   - '8'
+  - '7'
+  - '6'
 
 before_script:
   - npm prune
