Chore: Add Node 8 to Appveyor (#1987)

Author: nschonni

appveyor.yml

@@ -64,6 +64,9 @@
       - nodejs_version: 7
         GYP_MSVS_VERSION: 2015
         APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      - nodejs_version: 8
+        GYP_MSVS_VERSION: 2015
+        APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
 
   install:
     - ps: Install-Product node $env:nodejs_version $env:platform
@@ -145,6 +148,9 @@
       - nodejs_version: 7
         GYP_MSVS_VERSION: 2015
         APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      - nodejs_version: 8
+        GYP_MSVS_VERSION: 2015
+        APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
 
   install:
     - ps: Install-Product node $env:nodejs_version $env:platform