Add support for Bernoulli distribution

[hot9cups]

Go through the Gaussian distribution class, the Binomial class and the Exponential class which are subclasses of General distribution class.

I would like to expand this to include a fourth distribution, the Bernoulli Probability Distribution.
It should be able to calculate mean, standard deviation, and create basic plots like those in the classes I linked.
I suppose it's going to be quite similar to the Binomialdistribution class.