doc(README): add waffle.io info
doc(README): add waffle.io info

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expobrain/GitPython,gitpython-developers/gitpython,jeblair/GitPython,breavo/GitPython,breavo/GitPython,nvie/GitPython,gitpython-developers/gitpython,expobrain/GitPython,jeblair/GitPython,gitpython-developers/GitPython,nvie/GitPython,gitpython-developers/GitPython