Git submodule remove

Hello,

I was curious why git-submodule does not have an `rm` command. Currently I have to manually delete it from .gitmodules, .git/config, .git/modules/, etc. See [0].

I'd like to contribute my first patch to this project by adding this feature, but wanted to check first with the community if there's any particular reason it was chosen not to not be implemented, or if it's simply that nobody has gotten around to it - it seems to be a relatively common feature someone might want.

Anyway, please let me know if this is something that would be accepted, or if anyone has any comments or suggestions.

Thanks! Kalyan

[0] https://git.wiki.kernel.org/index.php/GitSubmoduleTutorial#Removal