Rank-Biased Overlap (RBO): a similarity measure for indefinite ranked lists

This code implements the RBO metric, as described in:

@article{wmz10:acmtois, author = "Webber, William and Moffat, Alistair and Zobel, Justin", title = "A similarity measure for indefinite rankings", journal = "ACM Transactions on Information Systems", year = {2010}, }