Repro-eval

**New feature:** metadata support

**New feature:** Break score ties (like it is implemented in `trec_eval`) for runs that are not added via `pytrec_eval`.

**Bugfix**: Avoid rounding errors related to Kendall's tau

- **New feature:** Faster implementation of the RBO (from the TREC Health Misinformation Track; see also: https://github.com/claclark/Compatibility).

- **New feature:** The normalized RMSE (nRMSE) can now be determined for reproduced runs. Use `nrmse()` with the `RpdEvaluator`.

- **New feature:** It is now possible to pass the paths of the run files to the function of each measure.
- More unit tests
- Minor bug fixes