[Pharo-project] Two simple chapters on numbers

Hi guys I want to share that with you. (may be I wrote some errors that you will spot I'm sure). I wrote two chapters for the next book: float (with the participation of Nicolas Cellier) and internal number representation (two complements and friend). I wrote that also for myself so that I can forget and just read it again and could say: ok this is that simple.... :) Stef