post-spawnfest

Hello, we've used `yamler` for our Spawnfest [project](https://github.com/HollyBrolly/nakaz) this year; as a result, we've went over the source code and "cleaned it up" a bit, do you think that would be useful to merge into upstream?

P. S.: Probably, removing `libyaml` was kind of harsh, but what's the point of keeping it in the repo, when the library is available in all the major distros.