Package welford implements a one-pass algorithm for computing mean and variance.
Knuth attributes this algorithm to B.P. Welford in The Art Of Computer Programming, Volume 2.
O(1) Space Complexity Ideal for Running Statistics
Based on: http://www.johndcook.com/standard_deviation.html and http://www.johndcook.com/blog/2008/09/26/comparing-three-methods-of-computing-standard-deviation/
Welford's Algorithm implementation for python 3+ using Rust