Test project for resource authorization

This pull request contains a new test project for the `Owin.ResourceAuthorization.WebApi` project.

The tests uses the `TestServer` from the `Microsoft.Owin.Testing`-package:

>This package contains a TestServer which can create an OWIN request processing pipeline and helpers to submit requests to the pipeline as if it is a real server. Requests made with these helpers never hit the network as they are processed directly in memory. Let’s try to implement the above same test using TestServer.
http://blogs.msdn.com/b/webdev/archive/2013/11/26/unit-testing-owin-applications-using-testserver.aspx

There are only a couple of tests for the `ResourceAuthorize` attribute just to be sure that I understand how it's supposed to work before I do some other modifications in another pull request.