Remove Visual Studio test config from Centroid.Tests project

I'm guessing the project was created as a Test Project, so VS added a bunch of stuff to the csproj file for its personal use. Not only are we not using any of it, it also kept Xamarin Studio from being able to open the project, because it didn't recognize the project type.

I *think* these changes just revert it back to a simple class library type. However, all I did was go through the csproj file and remove everything that looked related to testing, so I may have missed something or removed too much. Anyone know more about this?

I was able to open the project in XS after these changes, and run the tests.