Use YAML version traits in the parser

[Paalon]

Use version traits for most functions in the parser. We need to make conditional branches when processing a YAML version directive but this PR does not include it.

[kescobo]

This has identical title to #228, and seems to be on the same branch. Was that unintentional duplication? Given all of the merge commits here, and the overlap with other stuff, I'm guessing this could do with a rebase / force push