CI: test node version 8 (#50)

Author: aichbauer

Diff for: .travis.yml

@@ -2,8 +2,9 @@ language: node_js
 sudo: true
 dist: trusty
 node_js:
-  - "4"
-  - "6"
+  - 4
+  - 6
+  - 8
 install:
   - yarn
 script: npm test

Diff for: appveyor.yml

@@ -2,8 +2,9 @@
 environment:
   matrix:
     # node.js
-    - nodejs_version: "4"
-    - nodejs_version: "6"
+    - nodejs_version: 4
+    - nodejs_version: 6
+    - nodejs_version: 8
 
 # Install scripts. (runs after repo cloning)
 install: