Added a few statistical distances

Added Chi-square, Bhattacharya, and Intersection distances to compare distributions.
The function comment and behavior do not match. The comment makes no mention of renormalization. (dividing by \sum_i p_i and \sum_i q_). I think it's better to state that the distributions must sum to 1 and not normalize. I agree with your earlier statement that the distances don't seem to make sense if they don't sum to 1.