doc(changes): inform about new API
doc(changes): inform about new API

Relates to #446

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