Add examples and time complexity to `stats::combinatorics` (#306)
Add examples and time complexity to `stats::combinatorics` (#306)

* add examples to stats::combinatorics

* add time complexity

Co-authored-by: David Laehnemann <0c7948b6e77e16a7c2f08e676c85de2b1aa6fa69@hhu.de>
rust-bio/rust-bio