Support C# 6

Author: Hosch250

appveyor.yml

@@ -2,6 +2,10 @@ version: 2.0.{build}-{branch}
 build:
   verbosity: normal
 
+os: Visual Studio 2015
+install:
+- set PATH=C:\Program Files (x86)\MSBuild\14.0\Bin;%PATH%
+
 configuration: Release
 
 init:
@@ -14,8 +18,4 @@ notifications:
     X-Duga-Event: duga42
   on_build_success: true
   on_build_failure: true
-  on_build_status_changed: true
-
-os: Visual Studio 2015
-install:
-- set PATH=C:\Program Files (x86)\MSBuild\14.0\Bin;%PATH%
+  on_build_status_changed: true