Bugfix release

Bugfix release. Fixes some distribution issues and temporarily removes the PonPyg species.

Bug fixes:

• Pin the msprime and attrs packages to resolve some distribution problems (#366; @jgallowa07 and @gtsambos).

New features:

• Provide citations for the genome assembly (#359, #360; @andrewkern and @grahamgower).

Breaking changes:

• Temporarily remove the PonPyg species from the catalog to provide time to fix issues with genomes and multi-species models (#365).