Merge pull request #1273 from srowhani/chore/ci

chore(ci): update appveyor build matrix

Author: srowhani

appveyor.yml

@@ -5,8 +5,8 @@ init:
 # Test against this version of Node.js
 environment:
   matrix:
-    - nodejs_version: '4'
     - nodejs_version: '6'
+    - nodejs_version: '9'
       # Latest stable version of Node
     - nodejs_version: 'stable'