Update appveyor yaml to help correct issue with GitHub deplymnt (#76)

Signed-off-by: José Simões <[email protected]>

appveyor.yml

@@ -26,9 +26,9 @@ build_script:
     msbuild source\nanoFramework.Tools.VisualStudio.AppVeyorBuild.sln /p:Configuration=Release  /logger:"C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll"
 artifacts:
 - path: '**\bin\Release\*MSBuildSystem*.nupkg'
-  name: MSBuild System Nuget Package
+  name: MSBuild_System_Nuget_Package
 - path: '**\*.vsix'
-  name: VS extension
+  name: VS_extension
 deploy:
 - provider: NuGet
   api_key:
@@ -40,8 +40,7 @@ deploy:
   description: add description here
   auth_token:
     secure: DNixoFFE+pGlwyhj7McfZoln42vOmj0iY1iNV9zXEr3y0NpXlOIgL8k5ehzlFM1S
-  artifact: VS extension
+  artifact: VS_extension
   draft: true
   prerelease: true
-  force_update: false
-
+  force_update: true