Return XUnit status code from OpenCover

This change combines the test and code coverage passes to improve
overall build performance, without sacrificing accurate test status
reporting by AppVeyor.

Author: sharwell

appveyor.yml

@@ -9,8 +9,8 @@ before_build:
 build:
   project: StyleCopAnalyzers.sln
   verbosity: minimal
-after_test:
-- .\packages\OpenCover.4.6.166\tools\OpenCover.Console.exe -register:user -target:"%xunit20%\xunit.console.x86.exe" -targetargs:"C:\projects\stylecopanalyzers\StyleCop.Analyzers\StyleCop.Analyzers.Test\bin\Debug\StyleCop.Analyzers.Test.dll -noshadow -appveyor" -filter:"+[StyleCop*]*" -excludebyattribute:*.ExcludeFromCodeCoverage* -hideskipped:All -output:.\StyleCopAnalyzers_coverage.xml
+test_script:
+- .\packages\OpenCover.4.6.166\tools\OpenCover.Console.exe -register:user -target:"%xunit20%\xunit.console.x86.exe" -targetargs:"C:\projects\stylecopanalyzers\StyleCop.Analyzers\StyleCop.Analyzers.Test\bin\Debug\StyleCop.Analyzers.Test.dll -noshadow -appveyor" -returntargetcode -filter:"+[StyleCop*]*" -excludebyattribute:*.ExcludeFromCodeCoverage* -hideskipped:All -output:.\StyleCopAnalyzers_coverage.xml
 - "SET PATH=C:\\Python34;C:\\Python34\\Scripts;%PATH%"
 - pip install codecov
 - codecov -f "StyleCopAnalyzers_coverage.xml"