Make density calculation in calculateInfoGain use numpy

[TroyGustke]

Currently, the function uses plt.hist() to obtain density and it creates a histogram plot with it. This function can be easily replaced with np.histogram. I would recommend creating a np array for the bins by linspace of a specified region, then do two np.histogram functions to get the density of the prior and posterior with the same bins.
This section of code is not well commented, and not optimized. I recommend further corrections in the KL calculation as well.
Use the principle of do not break the code. Leave that code there, add yours, check the outputs of both, show A Savara, if I A Savara agrees everything is the same we can then delete the old code and merge.