yaml 2.0.0 incompatibilities

[srenatus]

Turns out it's not so simple: #172 as some thing we relied on have changed.

Do we need the new version? I can't tell.

cc @aron

[aron]

Hmm, I wouldn't think this is urgent unless there are security issues in the 1.x branch, I might actually have some time next week to look into this.