Added a few statistical distances

Added Chi-square, Bhattacharya, and Intersection distances to compare distributions.
Are you sure the order of these is the desired order? Wikipedia and Scipy both seem to imply it's usually it's  ChiSquare(observed, expected) and then it's (O[i] - E[i])^2 / E[i], which means it should be (p[i] - q[i])^2 / q[i].