build: Use node 8 only for CI

Andrey Okonetchnikov · Andrey Okonetchnikov · commit a5c6cad1b747 · 2017-07-19T14:40:46.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -5,9 +5,7 @@ cache:
 notifications:
   email: false
 node_js:
-  - '7'
-  - '6'
-  - '4'
+  - '8'
 before_script:
   - npm prune
 after_success:
