Fixing error this is causing in another project.

Not sure if this is the ideal way to solve this problem or not. This is being used as a submodule in another repo where this path becomes important. Ideally it would be externalized, but I don't see a way to do that in Unity. Another option would be to change how strangeioc-reversi is including the submodule, but it seems like there's a good structure set up there already.