added validation in methods. documentation more in line with math naming
Incompatible change with KeyBag renamed to BagHash fixed.

https://github.com/perl6/specs/commit/2845cf6aefdc9bd0baaefe956302a480fe
2a84db
Better explanation of how Markov chains work.
Documentation and comments cleanup
Add Андрей Андреевич Марков photo as icon
Protect against empty strings in feed and invalid length
Release as 1.0.