Optimize CoinSim; runs insanely fast now.
Optimize CoinSim; runs insanely fast now.

I used `numpy` to get an array of random floats and used `numexpr` to do the evaluation, then sum up the results.

The stuff runs insanely fast now, since it's all mathematical operations.

wei2912/bce-simulation,wei2912/bce-simulation,wei2912/bce-simulation,wei2912/bce-simulation