Added a few statistical distances

Added Chi-square, Bhattacharya, and Intersection distances to compare distributions.
Please refer to "The Earth Mover's Distance as a Metric for Image Retrieval" (page 3 under Histogram Intersection): https://www.cs.duke.edu/~tomasi/papers/rubner/rubnerTr98.pdf.
It is useful for partial matching of histograms when their areas are not equal. If the total areas of the two distributions are equal to 1, then (1-Intersection) is equivalent to the normalized L1 distance. I know this is used widely with image histograms, but I don't know about other applications.
I think we can remove this function, Minkowski distance would be more useful in general.