clean up, before looking at the lost ordered and ranged templates
more cleanup
start rangedseq impl from what i remember from my old scalaz based version. mainly tree ++ missing, have to put my head again into the hinze paper it seems
++ is in there (with all the toList and ::: nastiness of hinze/paterson), but somehow is wrong, probably mixed up :+ and +: at some point
woop, that was again the split versus span predicate inversion. findOverlap seems fine with simple cases. still need to thorough unit test