Tell AppVeyor to use Node.js 6.9.2

Author: daviwil

appveyor.yml

@@ -10,6 +10,7 @@ branches:
 
 install:
   - git clone https://github.com/PowerShell/PowerShellEditorServices.git ../PowerShellEditorServices
+  - ps: Install-Product node '6.9.2'
   - ps: |
       Install-PackageProvider -Name NuGet -MinimumVersion 2.8.5.201 -Force | Out-Null
       Install-Module InvokeBuild -RequiredVersion 3.2.1 -Scope CurrentUser -Force | Out-Null