Have to commit and push the change to the submodule reference for others to see it.

This updates the superproject to reflect that the new changes in the
submodule should now be used.  This allows us to wait for the opportune
moment to incorporate submodule changes into the superproject that
references it.

It is important to remember that you are working with two separate
repositories.  From the point of view of the superproject, a commit to a
submodule is just another unstaged change that needs to be committed.

Similarly, if you commit in a submodule, but forget to push, and then
commit and push that change to the superproject, the superproject will now
refer to a submodule commit that doesn't extist for anyone else.