Update build script

Author: ENikS

appveyor.yml

@@ -21,17 +21,14 @@ build:
 after_build:
 - cmd: NuGet pack
 
-before_test:
-- choco install opencover.portable
-- choco install codecov
-  
-test_script:
-- OpenCover.Console.exe -register:user -target:"C:\Program Files\dotnet\dotnet.exe" -targetargs:"test --framework net46 --verbosity q"
-
-after_test:
-- codecov -f "results.xml" 
-
 artifacts:
 - path: 'Unity.*.nupkg'
   name: 'Unity'
 
+# publish NuGet package on tag build
+deploy:
+- provider: NuGet
+  api_key:
+    secure: oy2bh5r6l2tktqiulxea6rpj73yb6cgelcmhx4sl5yjd44
+  on:
+    appveor_repo_tag: true