Add missing submodules and data to setup.py

[Vinye]

Hello!

Thanks for making this package. I want to apply this in my own project and I tried to install this as a git dependency using Poetry, because I'd prefer to use Poetry for all my dependency management.

Installation passed, but when I tried to import modules, it failed because submodules were missing. After looking at the setuptools documentation, I modified the setup.py configuration for finding packages and data files. Additionally, since there are git LFS files in this repo, I added a git lfs pull call to the setup.py script by adapting the code shown in this stackoverflow answer. The call assumes user has git LFS installed, otherwise it will fail and complain about missing git LFS.

I've tested that the proposed changes work by adding my local copy as a path dependency. The package gets installed to a Poetry-managed virtual environment with all the submodules and weight files. And running RetinaFacePredictor(threshold=0.8, device='cuda:0', model=RetinaFacePredictor.get_model('resnet50')) loaded the model without problems.

In the third commit I just fixed a small typo in requirements.txt while I was at it.

I'll make a similar pull request for the face_alignment package.