The purpose of this (XS) module is to calculate the median (or in principle also
other statistics) with confidence intervals on a sample. To do that, it uses a
technique called bootstrapping. In a nutshell, it resamples the sample a lot of
times and for each resample, it calculates the median. From the distribution of
medians, it then calculates the confidence limits.

In order to implement the confidence limit calculation, various other functions
had to be implemented efficiently (both algorithmically efficient and done in
C). These functions may be useful in their own right and are thus exposed to
Perl. Most notably, this exposes a median (and general selection) algorithm that
works in linear time as opposed to the trivial implementation that requires
O(n*log(n)).