`git ubuntu submit` improvements

[Florent 'Skia' Jacquet]

Hello there!

For the ones among you that use `git-ubuntu`, you might want to try out a better™ version of `git ubuntu submit`.
I have opened this MP[1] that tries to improve things a bit when used without arguments. Some testing and feedback would be most welcome, even if just to say "it works".

Thanks!
Skia

[1]: https://code.launchpad.net/~skia/git-ubuntu/+git/git-ubuntu/+merge/495893