zest.releaser doesn't seem to be compatible with git submodules. It makes a
fresh checkout of a tag, and then uploads a zip file of that, but in doing so
fails to run the commands required to initialize and update the submodules.

    git submodule init
    git submodule update 

I therefore instead, make sure the submodule is initialized and then run the
uploads manually.

python setup.py sdist --formats=zip upload -r plone
python setup.py sdist --formats=zip upload -r pypi
