GitLab

Moved all the includes to a subfolder yaml-cpp so they don't interfere with other libraries' includes

Refactored the operator >> and Node::Read default functions, as well as the conversion functions, to more easily read new types as keys (this uncovered an error, in example 2.11 of the spec)

Converted indexing to std::size_t, and fixed the Node templated overloads to properly index any index type (determining what is an index type is a bit of a hack - it should be is_convertible<T, std::size_t> (I think), but I just explicitly wrote down a list)

It's better organized now, I think - nodes only offer a single main way of getting the fundamental scalar (as a string), and now we can specialize a single template to read specific types.