consider functions for alpha/beta diversity per taxon

[zachary-foster]

Usually, diversity stats compare whole communities. Since there is usually a specific group of organisms being worked on (bacteria, fungi), this is implicty the diversity of a taxon. Therefore, we can abstract this to doing calculations on every taxon, with the value of the "root" being the entire "community". This should be possible using compare_groups and heat_tree_matrix. There might be patterns in specific subtaxa not present in their supertaxa.