Add how to use remote-submodules

[AndreiCherniaev]

• I provide my work under the project license.
• I grant such license of my work as is required for the purposes of future print editions to Ben Straub and Scott Chacon.

Changes

Current doc confuse me.
"There is another way to do this which is a little simpler, however. If you pass --recurse-submodules to the git clone command, it will automatically initialize and update each submodule in the repository, including nested submodules if any of the submodules in the repository have submodules themselves."
I add how to use --remote-submodules option. For example I clone repo with recursive flag
git clone --recurse-submodules https://github.com/apc-llc/moviemaker-cpp.git
but googletest submodule still has old version because --recurse-submodules option in fact don't do and update as doc promise. I also need --remote-submodules option.
git clone --recurse-submodules --remote-submodules https://github.com/apc-llc/moviemaker-cpp.git
Now googletest submodule has last version.

Context

git with submodule
Thanks https://stackoverflow.com/a/3797061/7915017