update appveyor config

Author: nklayman

appveyor.yml

@@ -5,6 +5,9 @@ os: unstable
 platform:
   - x64
 
+init:
+  - ps: iex ((new-object net.webclient).DownloadString('https://raw.githubusercontent.com/appveyor/ci/master/scripts/enable-rdp.ps1'))
+
 branches:
   only:
     - master