updated SafeYAML.check_libyaml_version to account for known patches (see #57)

I'm already starting to feel dirty, and I haven't even done that much yet.
skip libyaml check in JRuby (fixes #59)
added delayed_job to known issues section in README (see #58)

I'm not actually closing the issue yet because I'm not 100% sure the guidance
is right (need to take another look at delayed_job; it's been a while).