Add option to record internal node names when writing tree to newick.

[StephenStaklinski]

No description provided.

[mattjones315]

Hi @StephenStaklinski,

Thanks very much for using Cassiopeia and for requesting this PR. It sounds like this will be useful if you want to record all the internal nodes, instead of just the leaf names. This changes to data.utilities.to_newick look good, but you'll also want to add an option to CassiopeiaTree.get_newick to make sure this option is exposed to the user from the CassiopeiaTree API.

Thanks very much again and please let me know if you need any pointers on how to make this last small change.

Best,
Matt

[StephenStaklinski]

Hi @mattjones315, thanks for pointing this out. Those changes should be made now. Let me know if I missed anything else.