-Cubic interpolation is working. 
-Cubic interpolation is working. 

-I need to refactor some of the code for efficiency and memory. The cell fraction is only used in nearest and linear options.
-I need to throroughly test the cubic function. 
-I need to write 1d, 2d, 3d, and a 4d example. Use these as test cases.
jasonnicholson/regularizeNd,jasonnicholson/regularizeNd