meta: drop support for node@4

BREAKING CHANGE: node@4 is no longer supported

Author: zkat

.travis.yml

@@ -1,6 +1,6 @@
 language: node_js
 sudo: false
 node_js:
+  - "9"
   - "8"
   - "6"
-  - "4"

appveyor.yml

@@ -1,8 +1,8 @@
 environment:
   matrix:
+    - nodejs_version: "9"
     - nodejs_version: "8"
     - nodejs_version: "6"
-    - nodejs_version: "4"
 
 platform:
   - x64
@@ -17,5 +17,5 @@ test_script:
 
 matrix:
   fast_finish: true
-  
+
 build: off