Submodules are broken for outside contributors

Hi,

I'm trying to pull and build the repo to work on a patch for #563 but you've put git@github ssh references in for all your git submodules. That's a problem because that means anyone who isn't a member of all your repos can't just do a recursive clone or submodule update.

Can you please change the submodule references to use https instead of ssh, or alternately include a script or a list of required submodules so that an outside contributor can at least bootstrap this?

thank you,