improve cM awareness, especially in Interval
add script to compute the ancestry proportions on the filtered data
add debug print and switch to only compute chromosome 18 for speed
actually use the user input regarding the dataset filter
replace len builtin with length method on Interval and IBDEntry

The len builtin casts the return value of the __len__ magic method to
int. This is undesirable in the case of float Interval objects, e.g.
IBDEntry objects representing centimorgan.
replace reduce with for loop and add print statements
actually fix the zeros!

The bug was coming from one last place where interval_bp was being
erroneously used, namely the __len__ method of the match objects.
This method was replaced with a length method, returning an int or a
float, depending on the type of the IBDEntry underlying the match
object.
adjust runner scripts to use all the chromosomes, of the best data