divided random number generation into three (or four) separate, explicitly seeded RNGs
each ensemble member now runs in its own process to take advantage of multiple cores
ran code for t=5000; multiprocessing only saves about 20 percent of time; these seeds exhibit good clustered volatility tho
changed the method of plotting the ensemble of price series from histogram-from-above to regions between 1 percent and 99 percent, between 10 percent and 90 percent, etc; notably, this takes a long time to plot