Build: Add newer node targets to CI (#7)

Author: tchetwin

.travis.yml

@@ -1,6 +1,9 @@
 sudo: false
 language: node_js
 node_js:
+  - '12'
+  - '10'
+  - '8'
   - '6'
   - '5'
   - '4'

appveyor.yml

@@ -9,6 +9,10 @@ environment:
     - nodejs_version: "4"
     - nodejs_version: "5"
     - nodejs_version: "6"
+    - nodejs_version: "8"
+    - nodejs_version: "10"
+    # Waiting on https://github.com/appveyor/ci/issues/2921
+    # - nodejs_version: "12"
 
 install:
   - ps: Install-Product node $env:nodejs_version