Chronumental

What's Changed
* Refactor for new models by theosanderson in https://github.com/theosanderson/chronumental/pull/11


**Full Changelog**: https://github.com/theosanderson/chronumental/compare/v0.0.37...v0.0.38

What's Changed
* Explain when can't find ref point by theosanderson in https://github.com/theosanderson/chronumental/pull/9


**Full Changelog**: https://github.com/theosanderson/chronumental/compare/v0.0.36...v0.0.37

Allows use of per-site normalised distances and mutation rates. Keeps best parameters by default.

This release temporarily recommends the use of integer numbers of mutations, until we have added a `--genome_size` argument.