Allow submodules in `install.sh` lists

`install.sh` has a list of "modules" to "install" (stow) that it iterates through. Right now I have the "fortune" module that installs into the `~/lib` directory. This will become problematic in the future if we want to store other things into `~/lib`.

Find some way of everything playing along nicely. Off the top of my head, allowing for "submodules" might be a good way to resolve this, whereby main folders are expected and subfolders in a module are stowed.

This will likely take some reorganization of files.