create Scheme directory + init commit cardinality estimation
algorithm skeleton / helper functions / trailing-zeroes

This is a first draft based of "Cardinality estimation" based on Flajolet's papers. I have implemented some helper functions and trailing-zeroes which does some bitwise arithmetic. The main component is left to develop.
Update cardinality_estimation.rkt
helper function contracts + signature / corrected some typos.
Merge pull request #5 from aaronwinter/master

Algorithm to determine an estimation of the cardinality of a set using analytic combinatorics