only build packaging-related commits (#195)

* only build packaging-related commits

* include unit-tests per discussion in tracking issue

Author: MV10

appveyor.yml

@@ -6,6 +6,14 @@ build_script:
 test: off
 artifacts:
 - path: artifacts/Serilog.Sinks.Elasticsearch*.nupkg
+only_commits:
+  files:
+    - serilog-sinks-elasticsearch.sln
+    - src/Serilog.Sinks.Elasticsearch/
+    - nuget.config
+    - Build.ps1
+    - assets/
+    - test/Serilog.Sinks.Elasticsearch.Tests/
 deploy:
 - provider: NuGet
   api_key: