Initial version for code review

Because the initial development was occurring on master, there isn't an easy way to do code review. This pull exists solely as a means to code review the entire project. Any changes will be put straight into master and this pull will be closed and the `initial-code-review` branch deleted. All future development will use pull requests into master to facilitate code review.
> This get makes some assumptions about the way the user wants to use Hierarchy that I think should be documented (or they could just read the code).

Absolutely. This is exactly why this class isn't more fleshed out and is currently experimental. I added some notes explaining this: 7b1e77b9e45ef38fdb8db1afd18143478d4eefe9.