actually, VS2013 is supposed to be the .NET Framework target

Author: bodewig

appveyor.yml

@@ -1,15 +1,15 @@
 version: 2.7.0.{build}
 
 image:
-  - Visual Studio 2015
+  - Visual Studio 2013
   - Visual Studio 2017
 
 skip_tags: true
 
 for:
   - matrix:
       only:
-        - image: Visual Studio 2015
+        - image: Visual Studio 2013
     before_build:
       - appveyor DownloadFile https://dist.nuget.org/win-x86-commandline/v4.9.2/nuget.exe
       - appveyor DownloadFile https://raw.githubusercontent.com/appveyor/ci/master/scripts/nuget-restore.cmd