meta: update node version support

BREAKING CHANGE: node@4 is no longer supported

Author: zkat

.travis.yml

@@ -1,9 +1,10 @@
 # cipm currently relies on npm >5.4.0 to retrieve config
 before_install:
-  - npm i -g npm@^5.4.0
+  - npm i -g npm@>5.4.0
 language: node_js
 sudo: false
 node_js:
+  - "10"
+  - "9"
   - "8"
   - "6"
-  - "4"

appveyor.yml

@@ -1,16 +1,17 @@
 environment:
   matrix:
+    - nodejs_version: "10"
+    - nodejs_version: "9"
     - nodejs_version: "8"
     - nodejs_version: "6"
-    - nodejs_version: "4"
 
 platform:
   - x64
 
 install:
   - ps: Install-Product node $env:nodejs_version $env:platform
   - npm config set spin false
-  - npm i -g npm@^5.4.0
+  - npm i -g npm@>5.4.0
   - npm install
 
 test_script: