Skip AppVeyor when building on tags

appveyor.yml

@@ -17,3 +17,7 @@ build: false  # Not a C# project, build stuff at the test step instead.
 
 test_script:
   - C:\Python35\python -m tox
+
+# We don't deploy anything on tags with AppVeyor, we use Travis instead, so we
+# might as well save resources
+skip_tags: true