Document when to use safe_yaml vs YAML.safe_load

[movermeyer]

I was looking through my Gemfile.lock one day and noticed safe_yaml was there as a transitive dependency of another gem I was using.

The name safe_yaml made me concerned that I had been doing YAML parsing in an unsafe manner up until now.

After reading your README, it sounds like safe_yaml solves the same problem as YAML.safe_load, which left my wondering when would I use safe_yaml vs YAML.safe_load.

Consider adding a section to the introduction of the README answering this question?