Issues with the random number seed fixed

The random number seeding was not being done properly. I have fixed the code to use np.random's own set_state and get_state methods. I have checked that the random numbers generated are reproducible now.

I also patched bureau.py to use a separate random number generator while creating the probabilities plot. This avoids the random number generator in bureau interfering with the random number generator used by the agents. This should also guarantee reproducibility when SWAPSHOP.csh is run with or without the --fast option.