add version to Appveyor
diff --git a/appveyor.yml b/appveyor.yml
index a17ff15..87b8bf4 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,3 +1,5 @@
+version: 4.0-{build}
+
 os:
   - Visual Studio 2015