how to checkout proper submodules

[Kazu Yamamoto ( 山本和彦 )]

> There are a lot of things to recommend moving to github. I do hate
> (non-empty) merge commits, though, so I'm not a fan of github's pull
> request mechanism.

Please read "A successful Git branching model" to know why fast-forward
is not used recently.

	Git flow:
	http://nvie.com/posts/a-successful-git-branching-model/

Another relating article is here:

	Github flow:
	http://scottchacon.com/2011/08/31/github-flow.html

--Kazu