Fix test builds

[nbarbettini]

This PR contains a couple of changes:

• Removes the System.Web and ServiceStack serializers that were previously used for tests. (Deprecated in v3, replaced by Split NuGet package into few child packages to ease dependencies #76 eventually)
• Adds some duplicate tests to JWT.Tests.NETFramework, to sanity check that the library works from a .NET Framework (not .NET Core) project. It should always work, but tests are nice. 😄
• Fixes the package hint path issues from Fix tests nuget references #100. The solution should now build fine locally and on the CI server.

Resolves #108

[abatishchev]

Cool! The only concern is the code duplication between .NET and Core tests. Once one is changed, another has to be updated manually. Would it be possible to put them in a shared tests project and link from the platform specific projects?

[nbarbettini]

Good call. I forgot that it's possible to reference code files in another project. The latest change looks like it works on the build server.

[abatishchev]

Would it be better to add those files as links? i.e. https://i-msdn.sec.s-msft.com/dynimg/IC625712.png

[nbarbettini]

I tried that at first, but xUnit wouldn't discover the tests in the project that used links.

[abatishchev]

That's odd. Let me try locally, I need to see with my own eyes to fully believe :) Because it shouldn't care since suppose to scan output assembly, not input project.

[abatishchev]

Can you please take a look on the latest changes? Would this work, how do you think?

[abatishchev]

Never mind, seems to work fine now

[latchkostov]

Are you guys going to merge here?