Sequel support

Support for the Sequel ORM.
Looks great, although at I didn't yet grasp how exactly it works in the context of this issue.
I remember that there was an infinite recursion happening somewhere but now I cannot reproduce it by tests if I remove line 76. Which is weird. Were you able to reproduce that? I think there was a stack level too deep error, but it seems I didn't have a spec for it or something changed in this regard when I did the rebase 2 weeks ago. We should probably make a test for that so we know the new solution also prevents that problem (even if issue was actually made irrelevant by some other changes you made before my rebase).