Dropped Node 4 support

ognus · ognus · commit 3866fa05e57d · 2018-11-17T20:15:57.000+09:00
diff --git a/.travis.yml b/.travis.yml
@@ -3,7 +3,7 @@ addons:
   chrome: stable
 language: node_js
 node_js:
-  - "4"
   - "6"
   - "8"
-  - "9"
+  - "10"
+  - "11"
