Build: Add node 9 to CI matrices

Author: mcollina

.travis.yml

@@ -1,6 +1,7 @@
 sudo: required
 language: node_js
 node_js:
+  - '9'
   - '8'
   - '6'
   - '5'

appveyor.yml

@@ -10,6 +10,7 @@ environment:
     - nodejs_version: "5"
     - nodejs_version: "6"
     - nodejs_version: "8"
+    - nodejs_version: "9"
 
 install:
   - ps: Install-Product node $env:nodejs_version