Temporary workaround for pester issue causing build to get stuck

Author: KarolKaczmarek

appveyor.yml

@@ -3,7 +3,7 @@
 #---------------------------------# 
 version: 1.1.{build}.0
 install: 
-  - cinst -y pester
+  - cinst -y pester --version 3.3.13
   - git clone https://github.com/PowerShell/DscResource.Tests
   - ps: Push-Location
   - cd DscResource.Tests