Rough draft of the Committing guidelines

This is the rough draft and will have many more changes as we flesh out exactly what we want our committing standards to be.
Note: the Robottelo Standards link will be broken until we create that document.
It's still good to plan ahead a little bit and explicitly state what you're planning on writing, at least at a high level. For example, I'm wondering whether the contents of `code-standards.rst` will overlap with a document containing reviewer guidelines. Writing down some TODOs forces the writer to think through those issues a little bit.