Testing - Check build dependencies and sequence for OutOfProcess tests

From @eeaston:

> Another gotchya I think I’m seeing is that when running the test using out of process mode, I need to do a project->build in visual studio, instead of just running the test and expecting it to do the build for me. If I don’t do this, then it uses the previous built binaries.

If this is tricky to fix we should at least document it in the [Readme](https://github.com/Excel-DNA/DeveloperTools/blob/master/ExcelDna.Testing/Readme.md).