Make xunit runner task take IncludeTraits and ExcludeTraits properties
Add error to build.cmd when running in a non DevEnv command prompt.

Update links to developer guide in error messages to new location
on the dotnet/corefx wiki.
Merge remote-tracking branch 'kr/XunitTraits'
Cause appveyor to run CI build in Dev12 developer command prompt.
Cause build.cmd to set errorlevel to 1 on failed prereqs
Cause depending.targets to find NuGet.config file in correct location
Do not run outerloop or failing tests (with issue)
Upgrade xunit.runners version
Merge pull request #24 from krwq/donotrunouterloopandfailing

Do not run outerloop or failing tests (with issue)
Merge pull request #25 from FiveTimesTheFun/nugetconfig-fix

Cause depending.targets to find NuGet.config file in correct location