ctest setup checking

[balarsen]

Can you take a look at bc2aff1246 and do cmake using -DBUILD_TESTS=ON.

• did I do the BUILD_TESTS=ON correctly? Do we want to do this at all?
• in Tests/ did I do CMakeLists.txt correctly, is this how we want to do this?
• in Tests is that a reasonable way to do the tests? Or do you have a better one?

[nicolasbock]

I think this looks good. At some point we could think about using a unit test framework, but I think for now it's ok without one.