chore: remove nodejs 4 support

NoNameProvided · web-flow · commit 9854ed7d1e1e · 2018-01-27T14:10:43.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,9 +1,8 @@
 language: node_js
 node_js:
   - stable
+  - 8
   - 6
-  - 5
-  - 4
 
 after_success:
   - bash <(curl -s https://codecov.io/bash)
