By Elizabeth Hemmerdinger What really started the world-wide financial nuclear reaction?  There’s been no loud explosion, no visible flames, no pore-clogging airborne toxins, but Michael Lewis, the documentarian of Wall Street’s excesses of the ‘80’s in his 1990 book Liar’s Poker, offers us an explanation for the recent financial bloodbath. The End of the Wall Street Boom,  on Portfolio.com, is…