Spiral Matrix function for Ulam Spirals
The main function ulam(w, h, x, y) generates a spiral matrix of width w and height h, and tells you what the value is at position x, y in that matrix. Note that 1,1 is in the top left corner of a matrix. See [Ulam Spiral rectangular grid construction] (http://en.wikipedia.org/wiki/Ulam_spiral#Construction) for more details.
This was mostly a mental exercise, and something for [Joseph] (https://github.com/jcla1) to use.