Statistics library

[dsimcha]

== Quote from BCS (ao at pathlink.com)'s article
> Even better would be getting it in both Phobos and Tango. Shouldn't be hard
> as I can't think it should depend on much.

First, Tango needs to be ported to D2 (I realize that this is happening) or my
code needs to be ported to D1.  Anyhow, here are the dependencies:

Non-trivial, i.e. in several places:
std.math, std.traits, std.functional, some custom sorting functions I wrote, which
could just be included

Trivial, i.e. in only one or two small places, pretty sure Tango has a drop-in
replacement
std.bigint (for factorial, although all functions that actually use a factorial
are calculated in log space, and therefore don't depend on this), std.algorithm
(for swap, isSorted), std.random