I mean this is trivial but I don't want to add this to ES. It's pretty much broken unless you exactly know how it works internally. What I mean is that you can't call `#next()` or `docs()` since it doesn't seek. I think we can work towards this but it should have all the functions supported.  I think we should cache both `ttf` and `df` and put a boolean if a `real` seek is needed and then do the seek if one of the other methods i called. makes sense? Other than that I think this is the way to go