No documentation about git init

Created by: ryancogswell

I was surprised when trying out create-react-app 2 that the new app I created had its own git repository. I didn't see any mention of this in the user guide or in the "what's new" portion of the blog post. Eventually I found the code changes from @mauricedb for issue #1288. I don't have a problem with the new behavior, but it should be documented somewhere.