Update readme with note on HACKING doc
Update readme with note on HACKING doc

adamlincoln/Bookie,adamlincoln/Bookie,adamlincoln/Bookie,skmezanul/Bookie,teodesson/Bookie,charany1/Bookie,teodesson/Bookie,skmezanul/Bookie,bookieio/Bookie,teodesson/Bookie,bookieio/Bookie,GreenLunar/Bookie,GreenLunar/Bookie,skmezanul/Bookie,charany1/Bookie,wangjun/Bookie,wangjun/Bookie,charany1/Bookie,GreenLunar/Bookie,wangjun/Bookie,teodesson/Bookie,adamlincoln/Bookie,skmezanul/Bookie,bookieio/Bookie,bookieio/Bookie,GreenLunar/Bookie,wangjun/Bookie