Build: Add node 8 & 10 to build matrix

Author: phated

Diff for: .travis.yml

@@ -1,6 +1,8 @@
 sudo: false
 language: node_js
 node_js:
+  - '10'
+  - '8'
   - '6'
   - '5'
   - '4'

Diff for: appveyor.yml

@@ -9,6 +9,8 @@ environment:
     - nodejs_version: "4"
     - nodejs_version: "5"
     - nodejs_version: "6"
+    - nodejs_version: "8"
+    - nodejs_version: "10"
 
 install:
   - ps: Install-Product node $env:nodejs_version