Fix NUnit path

Add -beta to NuGet version

HtmlSanitizer/HtmlSanitizer.nuspec

@@ -2,7 +2,7 @@
 <package >
   <metadata>
     <id>$id$</id>
-    <version>$version$</version>
+    <version>$version$-beta</version>
     <title>$title$</title>
     <authors>$author$</authors>
     <owners>$author$</owners>

appveyor.yml

@@ -1,4 +1,4 @@
-version: 3.1.{build}
+version: 3.2.{build}
 install:
   - nuget restore
 configuration: Release
@@ -31,7 +31,7 @@ build:
 test_script:
   - nuget.exe install OpenCover -ExcludeVersion
   - nuget.exe install NUnit.Runners -ExcludeVersion
-  - OpenCover\tools\OpenCover.Console.exe -register:user -filter:"+[HtmlSanitizer]*" -target:"NUnit.Console\tools\nunit3-console.exe" "-targetargs:/domain:single HtmlSanitizer.Tests\bin\release\HtmlSanitizer.Tests.dll" -returntargetcode -hideskipped:All -output:coverage.xml
+  - OpenCover\tools\OpenCover.Console.exe -register:user -filter:"+[HtmlSanitizer]*" -target:"NUnit.ConsoleRunner\tools\nunit3-console.exe" "-targetargs:/domain:single HtmlSanitizer.Tests\bin\release\HtmlSanitizer.Tests.dll" -returntargetcode -hideskipped:All -output:coverage.xml
   - "SET PATH=C:\\Python34;C:\\Python34\\Scripts;%PATH%"
   - pip install codecov
   - codecov -f "coverage.xml"