You can clone with
HTTPS or Subversion.
I installed your extension but I'm not sure wether it is calculating quantiles correct... Aren't you calculating "equal intervals" instead of "quantiles" (http://www.ncgia.ucsb.edu/cctp/units/unit47/html/comp_class.html)
I checked it on my dataset with multiple duplicate values and I get a wrong result. As far as I know duplicate values only are calculated once. Correct me if I'm missing something.