Added submodules to repo.

[gedex]

For some reason cloning the repo and then update the submodule with git submodule update --init --recursive won't do nothing. Same thing if you clone it for the first time with --recursive. It might be specific to git version. I'm using git 2.3.2.

This change will add the submodule path into the repo so that cloning with --recursive or update it with git submodule update --init --recursive works.